Yes, Some People Can Be Both Fat and Fit

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People can be obese but metabolically healthy and fit, with no greater risk of developing or dying from cardiovascular disease or cancer than normal weight people, according to the largest study ever to have investigated this seeming paradox.
The findings show there is a subset of obese people who are metabolically healthy — they don’t suffer from conditions such as insulin resistance, diabetes and high cholesterol or blood pressure — and who have a higher level of fitness, as measured by how well the heart and lungs perform, than other obese people. Being obese does not seem to have a detrimental effect on their health, and doctors should bear this in mind when considering what, if any, interventions are required, say the researchers.
«It is well known that obesity is linked to a large number of chronic disease such as cardiovascular problems and cancer. However, there appears to be a sub-set of obese people who seem to be protected from obesity-related metabolic complications,» said the first author of the study, Dr Francisco Ortega (PhD). «They may have greater cardio-respiratory fitness than other obese individuals, but, until now, it was not known the extent to which these metabolically healthy but obese people are at lower risk of diseases or premature death.»
Dr Ortega is currently a research associate affiliated to the Department of Physical Activity and Sport, University of Granada (Spain), and at the Department of Biosciences and Nutrition, Karolinska Institutet (Stockholm, Sweden); but the project and investigation took place at the University of South Carolina (Columbia, USA) under the direction of Professor Steven Blair, who is responsible for the long-running «Aerobics Center Longitudinal Study» (ACLS) which provided the 43,265 participants for this current analysis.
The participants were recruited to the ACLS between 1979 and 2003. They completed a detailed questionnaire, including information on their medical and lifestyle history, and they had a physical examination that included a treadmill test to assess cardio-respiratory fitness and measurements of height, weight, waist circumference, and their percentage of body fat. Body fat percentage (BF%) was measured either by calculating the amount of water displaced when the person was completely submerged (the method that is considered the most accurate), or by taking the sum of seven skin fold measures (when folds of skin are pinched between measurement callipers). Blood pressure, cholesterol and fasting glucose levels were also measured. The study participants were followed until they died or until the end of 2003.
Dr Ortega and his colleagues found that 46% of the obese participants were metabolically healthy. After adjusting for several confounding factors, including fitness, the metabolically healthy but obese people had a 38% lower risk of death from any cause than their metabolically unhealthy obese peers, while no significant difference was seen between the metabolically healthy but obese and the metabolically healthy, normal weight participants. The risk of developing or dying from cardiovascular disease or cancer was reduced by between 30-50% for the metabolically healthy but obese people, and there were no significant differences observed between them and the metabolically healthy, normal weight participants.
«Our study suggests that metabolically healthy but obese people have a better fitness level than the rest of obese individuals. Based on the data that our group and others have collected over years, we believe that getting more exercise broadly and positively influences major body systems and organs and consequently contributes to make someone metabolically healthier, including obese people.
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Yes, Some People Can Be Both Fat and Fit

Escrito por

People can be obese but metabolically healthy and fit, with no greater risk of developing or dying from cardiovascular disease or cancer than normal weight people, according to the largest study ever to have investigated this seeming paradox.
The findings show there is a subset of obese people who are metabolically healthy — they don’t suffer from conditions such as insulin resistance, diabetes and high cholesterol or blood pressure — and who have a higher level of fitness, as measured by how well the heart and lungs perform, than other obese people. Being obese does not seem to have a detrimental effect on their health, and doctors should bear this in mind when considering what, if any, interventions are required, say the researchers.
«It is well known that obesity is linked to a large number of chronic disease such as cardiovascular problems and cancer. However, there appears to be a sub-set of obese people who seem to be protected from obesity-related metabolic complications,» said the first author of the study, Dr Francisco Ortega (PhD). «They may have greater cardio-respiratory fitness than other obese individuals, but, until now, it was not known the extent to which these metabolically healthy but obese people are at lower risk of diseases or premature death.»
Dr Ortega is currently a research associate affiliated to the Department of Physical Activity and Sport, University of Granada (Spain), and at the Department of Biosciences and Nutrition, Karolinska Institutet (Stockholm, Sweden); but the project and investigation took place at the University of South Carolina (Columbia, USA) under the direction of Professor Steven Blair, who is responsible for the long-running «Aerobics Center Longitudinal Study» (ACLS) which provided the 43,265 participants for this current analysis.
The participants were recruited to the ACLS between 1979 and 2003. They completed a detailed questionnaire, including information on their medical and lifestyle history, and they had a physical examination that included a treadmill test to assess cardio-respiratory fitness and measurements of height, weight, waist circumference, and their percentage of body fat. Body fat percentage (BF%) was measured either by calculating the amount of water displaced when the person was completely submerged (the method that is considered the most accurate), or by taking the sum of seven skin fold measures (when folds of skin are pinched between measurement callipers). Blood pressure, cholesterol and fasting glucose levels were also measured. The study participants were followed until they died or until the end of 2003.
Dr Ortega and his colleagues found that 46% of the obese participants were metabolically healthy. After adjusting for several confounding factors, including fitness, the metabolically healthy but obese people had a 38% lower risk of death from any cause than their metabolically unhealthy obese peers, while no significant difference was seen between the metabolically healthy but obese and the metabolically healthy, normal weight participants. The risk of developing or dying from cardiovascular disease or cancer was reduced by between 30-50% for the metabolically healthy but obese people, and there were no significant differences observed between them and the metabolically healthy, normal weight participants.
«Our study suggests that metabolically healthy but obese people have a better fitness level than the rest of obese individuals. Based on the data that our group and others have collected over years, we believe that getting more exercise broadly and positively influences major body systems and organs and consequently contributes to make someone metabolically healthier, including obese people.
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Study: People can be fat yet fit

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People can be obese yet physically healthy and fit and at no greater risk of heart disease or cancer than normal weight people, say researchers.

The key is being «metabolically fit», meaning no high blood pressure, cholesterol or raised blood sugar, and exercising, according to experts.

Looking at data from over 43,000 US people they found that being overweight per se did not pose a big health risk.

The results are published in the European Heart Journal.

In the study at the University of South Carolina, more than a third of the participants were obese.

Of these 18,500, half were assessed as metabolically healthy after a physical examination and lab tests.

This subset of metabolically healthy obese people who did not suffer from conditions such as diabetes, high cholesterol or high blood pressure, were generally fitter and exercised more than the other obese people.

And their risk of developing or dying from cardiovascular disease or cancer was identical to people of ideal weight and was half that of «metabolically less fit» obese people.

Lead researcher Dr Francisco Ortega, who currently works at the University of Granada in Spain, said the findings show that getting more exercise can keep you healthier, even if you still carry a bit of extra weight.

«This research highlights once again the important role of physical fitness as a health marker.»

Most of the men and women in the study came from a similar background, meaning the results may not apply to everyone. They were mostly Caucasian, well educated, and worked in executive or professional positions.

Amy Thompson, of the British Heart Foundation, said: «In the majority of cases, obesity is an undeniable risk factor for developing coronary heart disease. However, these studies remind us that it is not always your weight that’s important, but where you carry fat and also how it affects your health and fitness.

«It is particularly important to be aware of your weight if you are carrying excess fat around your middle. The fat cells here are really active, producing toxic substances that cause damage which can lead to heart disease.

«Maintaining a healthy diet with lots of physical activity can help to slim you down as well as reduce your risk of heart health problems.

«But don’t get too caught up on the numbers on the scale. Calculating your body mass index and measuring your waist are great ways to keep on track. If you are concerned about your weight and want to make changes to your lifestyle, make an appointment with your GP to talk it through.»

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Study: People can be fat yet fit

Escrito por

People can be obese yet physically healthy and fit and at no greater risk of heart disease or cancer than normal weight people, say researchers.

The key is being «metabolically fit», meaning no high blood pressure, cholesterol or raised blood sugar, and exercising, according to experts.

Looking at data from over 43,000 US people they found that being overweight per se did not pose a big health risk.

The results are published in the European Heart Journal.

In the study at the University of South Carolina, more than a third of the participants were obese.

Of these 18,500, half were assessed as metabolically healthy after a physical examination and lab tests.

This subset of metabolically healthy obese people who did not suffer from conditions such as diabetes, high cholesterol or high blood pressure, were generally fitter and exercised more than the other obese people.

And their risk of developing or dying from cardiovascular disease or cancer was identical to people of ideal weight and was half that of «metabolically less fit» obese people.

Lead researcher Dr Francisco Ortega, who currently works at the University of Granada in Spain, said the findings show that getting more exercise can keep you healthier, even if you still carry a bit of extra weight.

«This research highlights once again the important role of physical fitness as a health marker.»

Most of the men and women in the study came from a similar background, meaning the results may not apply to everyone. They were mostly Caucasian, well educated, and worked in executive or professional positions.

Amy Thompson, of the British Heart Foundation, said: «In the majority of cases, obesity is an undeniable risk factor for developing coronary heart disease. However, these studies remind us that it is not always your weight that’s important, but where you carry fat and also how it affects your health and fitness.

«It is particularly important to be aware of your weight if you are carrying excess fat around your middle. The fat cells here are really active, producing toxic substances that cause damage which can lead to heart disease.

«Maintaining a healthy diet with lots of physical activity can help to slim you down as well as reduce your risk of heart health problems.

«But don’t get too caught up on the numbers on the scale. Calculating your body mass index and measuring your waist are great ways to keep on track. If you are concerned about your weight and want to make changes to your lifestyle, make an appointment with your GP to talk it through.»

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Study: People can be fat yet fit

Escrito por

People can be obese yet physically healthy and fit and at no greater risk of heart disease or cancer than normal weight people, say researchers.

The key is being «metabolically fit», meaning no high blood pressure, cholesterol or raised blood sugar, and exercising, according to experts.

Looking at data from over 43,000 US people they found that being overweight per se did not pose a big health risk.

The results are published in the European Heart Journal.

In the study at the University of South Carolina, more than a third of the participants were obese.

Of these 18,500, half were assessed as metabolically healthy after a physical examination and lab tests.

This subset of metabolically healthy obese people who did not suffer from conditions such as diabetes, high cholesterol or high blood pressure, were generally fitter and exercised more than the other obese people.

And their risk of developing or dying from cardiovascular disease or cancer was identical to people of ideal weight and was half that of «metabolically less fit» obese people.

Lead researcher Dr Francisco Ortega, who currently works at the University of Granada in Spain, said the findings show that getting more exercise can keep you healthier, even if you still carry a bit of extra weight.

«This research highlights once again the important role of physical fitness as a health marker.»

Most of the men and women in the study came from a similar background, meaning the results may not apply to everyone. They were mostly Caucasian, well educated, and worked in executive or professional positions.

Amy Thompson, of the British Heart Foundation, said: «In the majority of cases, obesity is an undeniable risk factor for developing coronary heart disease. However, these studies remind us that it is not always your weight that’s important, but where you carry fat and also how it affects your health and fitness.

«It is particularly important to be aware of your weight if you are carrying excess fat around your middle. The fat cells here are really active, producing toxic substances that cause damage which can lead to heart disease.

«Maintaining a healthy diet with lots of physical activity can help to slim you down as well as reduce your risk of heart health problems.

«But don’t get too caught up on the numbers on the scale. Calculating your body mass index and measuring your waist are great ways to keep on track. If you are concerned about your weight and want to make changes to your lifestyle, make an appointment with your GP to talk it through.»

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Obesity ‘not necessarily a sign of poor metabolic health’

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A new study published in the European Heart Journal has highlighted the fact that it is possible to be obese while remaining metabolically fit and healthy.

Analysis carried out at by an international team based at the University of South Carolina – which assessed data from 43,265 people – has shone a spotlight on the subset of obese people who are at no greater risk of developing or dying from cardiovascular disease or cancer than people of a normal weight.

These subjects were found to be free of conditions such as insulin resistance, diabetes and high cholesterol or blood pressure, while their hearts and lungs also performed better than those of other obese people.

According to the researchers, the existence of this subset of people needs to be borne in mind by doctors when assessing treatment priorities.

Dr Francisco Ortega, first author of the study and a research associate affiliated with the University of Granada, said: «Our data supports the idea that interventions might be more urgently needed in metabolically unhealthy and unfit obese people, since they are at a higher risk.»

This comes after a report from the University of California – Los Angeles found that overweight people are often at a lower risk of suffering adverse outcomes from heart failure than slimmer patients, despite their higher risk of developing heart disease.

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Obesity ‘not necessarily a sign of poor metabolic health’

Escrito por

A new study published in the European Heart Journal has highlighted the fact that it is possible to be obese while remaining metabolically fit and healthy.

Analysis carried out at by an international team based at the University of South Carolina – which assessed data from 43,265 people – has shone a spotlight on the subset of obese people who are at no greater risk of developing or dying from cardiovascular disease or cancer than people of a normal weight.

These subjects were found to be free of conditions such as insulin resistance, diabetes and high cholesterol or blood pressure, while their hearts and lungs also performed better than those of other obese people.

According to the researchers, the existence of this subset of people needs to be borne in mind by doctors when assessing treatment priorities.

Dr Francisco Ortega, first author of the study and a research associate affiliated with the University of Granada, said: «Our data supports the idea that interventions might be more urgently needed in metabolically unhealthy and unfit obese people, since they are at a higher risk.»

This comes after a report from the University of California – Los Angeles found that overweight people are often at a lower risk of suffering adverse outcomes from heart failure than slimmer patients, despite their higher risk of developing heart disease.

Descargar

Obesity ‘not necessarily a sign of poor metabolic health’

Escrito por

A new study published in the European Heart Journal has highlighted the fact that it is possible to be obese while remaining metabolically fit and healthy.

Analysis carried out at by an international team based at the University of South Carolina – which assessed data from 43,265 people – has shone a spotlight on the subset of obese people who are at no greater risk of developing or dying from cardiovascular disease or cancer than people of a normal weight.

These subjects were found to be free of conditions such as insulin resistance, diabetes and high cholesterol or blood pressure, while their hearts and lungs also performed better than those of other obese people.

According to the researchers, the existence of this subset of people needs to be borne in mind by doctors when assessing treatment priorities.

Dr Francisco Ortega, first author of the study and a research associate affiliated with the University of Granada, said: «Our data supports the idea that interventions might be more urgently needed in metabolically unhealthy and unfit obese people, since they are at a higher risk.»

This comes after a report from the University of California – Los Angeles found that overweight people are often at a lower risk of suffering adverse outcomes from heart failure than slimmer patients, despite their higher risk of developing heart disease.

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A subset of obese are more fit

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There is a subset of obese people who are metabolically healthy and fit and have no greater risk of heart disease or cancer, researchers in Spain say.

The study, published in the European Heart Journal, said this group of people didn’t suffer from conditions such as insulin resistance, diabetes and high cholesterol or blood pressure — defined as metabolic syndrome — and had a higher level of fitness, as measured by how well the heart and lungs perform, than other obese people.

«It is well known that obesity is linked to a large number of chronic diseases such as cardiovascular problems and cancer. However, there appears to be a sub-set of obese people who seem to be protected from obesity-related metabolic complications,» first author Dr. Francisco Ortega of the University of Granada said in a statement.

«Until now, it was not known the extent to which these metabolically healthy but obese people are at lower risk of diseases or premature death.»

The investigation took place at the University of South Carolina in Columbia under the direction of Steven Blair, who is responsible for the long-running Aerobics Center Longitudinal Study, which provided the 43,265 participants for this current analysis from 1979 to 2003.

The study found 46 percent of the obese participants were metabolically healthy and they had a 38 percent lower risk of death from any cause than their metabolically unhealthy obese peers.

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A subset of obese are more fit

Escrito por

There is a subset of obese people who are metabolically healthy and fit and have no greater risk of heart disease or cancer, researchers in Spain say.

The study, published in the European Heart Journal, said this group of people didn’t suffer from conditions such as insulin resistance, diabetes and high cholesterol or blood pressure — defined as metabolic syndrome — and had a higher level of fitness, as measured by how well the heart and lungs perform, than other obese people.

«It is well known that obesity is linked to a large number of chronic diseases such as cardiovascular problems and cancer. However, there appears to be a sub-set of obese people who seem to be protected from obesity-related metabolic complications,» first author Dr. Francisco Ortega of the University of Granada said in a statement.

«Until now, it was not known the extent to which these metabolically healthy but obese people are at lower risk of diseases or premature death.»

The investigation took place at the University of South Carolina in Columbia under the direction of Steven Blair, who is responsible for the long-running Aerobics Center Longitudinal Study, which provided the 43,265 participants for this current analysis from 1979 to 2003.

The study found 46 percent of the obese participants were metabolically healthy and they had a 38 percent lower risk of death from any cause than their metabolically unhealthy obese peers.

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Can you really be both ‘fat and fit?’

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People «can be obese yet physically healthy and fit and at no greater risk of heart disease or cancer», according to BBC News.
This counterintuitive headline stems from a study that was assessing health outcomes for people who were obese but relatively fit, with only one or no risk factors for «metabolic syndrome». Metabolic syndrome is diagnosed when people have multiple risk factors, such as high blood pressure, that make them more prone to diabetes or cardiovascular disease (CVDs).
Researchers found that the «metabolic healthy» obese group were significantly less likely to develop a CVD or cancer, or die as a result, than people who were similarly obese but were judged to be «metabolic unhealthy». In fact the risks of CVDs and cancers in the «metabolic healthy but obese» group were broadly similar to people with a healthy weight.
However, the research should not be interpreted to mean that being obese is healthy. Waist circumference size is also a risk factor for CVDs, so ideally you should be aiming to have a circumference of less than 94cm (37in) if you’re a man and less than 80cm (31.5in) if you’re a woman.
The research actually tells us very little that is useful in how fitness levels can affect CVD and cancer risk and whether it is possible to be both «fat and fit».
The main implication of the research is that factors other than weight need to be taken in account when assessing these types of health risks.

 

Where did the story come from?

The study was carried out by researchers from the Karolinska Institute, Sweden, the University of Granada, Spain and the University of South Carolina, USA. The research was funded by the National Institutes of Health, the Spanish Ministry of Science and Innovation, the Swedish Heart-Lung Foundation and the Coca-Cola Company (the funding from Coca-Cola was given as an unrestricted grant; in other words «no strings attached»).
The study was published in the peer-reviewed European Heart Journal.

The media reflected the study findings accurately, but the newspaper headlines should not be interpreted to mean that being obese is healthy. A relevant health message that could have been added is that regular exercise can benefit you even if you remain overweight or obese despite your best efforts to lose weight.

What kind of research was this?

This was a cohort study aiming to look at the health of obese individuals who are metabolically healthy and without additional risk factors for CVDs. These were described by the researchers as people with «uncomplicated obesity».
The researchers said that there is uncertainty over the extent to which metabolic health in obese people can influence the risk of CVDs and overall mortality. This is what they aimed to examine.
They decided to examine two theories:
Metabolically healthy but obese individuals have a higher fitness level than obese individuals with metabolic abnormalities.
Metabolically healthy obese people have reduced risk of CVDs, cancer and mortality compared with obese individuals with metabolic abnormalities – the «theoretically unhealthiest group».
In this study, fitness (according to a treadmill test), obesity and metabolic risk factors all appear to have been measured at one point at the start of the study.
But it is difficult to tell how representative this one-off treadmill test is of the overall fitness level of an obese person, particularly as we don’t know how long the person has been obese for.
Measurements on obesity and metabolic health appear to be more reliable than those on fitness.

What did the research involve?

This was an analysis of the Aerobics Center Longitudinal Study (ACLS) which recruited predominantly white professional individuals between 1979 and 2003.
At the time of recruitment a number of assessements were carried out, including:
asking participants to complete a health questionnaire, including medical history and lifestyle habits (such as smoking and alcohol)
a physical examination (including measurement of BMI, body fat percentage and blood pressure) and blood tests taken for fasting blood sugar and lipids (triglycerides and high-density lipoprotein (HDL) «good» cholesterol)
They also performed an exercise treadmill test where they were asked to walk or jog slowly on a treadmill that increases its incline gradually. The test is then ended when the participants feel that they no longer have the stamina to continue (this type of test is known as the Balke treadmill protocol).
A person was defined as metabolically healthy if they met none or only one of the following criteria:
high blood pressure (≥130/85 mmHg)
high blood triglycerides (≥150 mg/dL)
low HDL «good» cholesterol (<40 and 50 mg/dL in men and women, respectively)
high fasting blood sugar level (≥100 mg/dL)
In addition, people with normal blood pressure or fasting blood sugar at the examination, but who reported a history of previously diagnosed high blood pressure or diabetes, were also classed as having these metabolic risk factors.
Participants were followed from recruitment to the end of 2003. Information on mortality came from the National Death Index. Data on non-fatal cardiovascular disease events came from the responses to health surveys in 1982, 1999 and 2004. There was said to be a 65% response rate across surveys.
Eligible participants had no history of cardiovascular disease or cancer at study start (baseline); had complete baseline data on body composition, metabolic risk factors and fitness and completed at least one year of follow-up for health and mortality outcomes.

What were the basic results?

A total 43,265 participants were included in the study (average age 44), a quarter of whom were women.
Of these:
5,649 were obese (13% of the cohort) according to the standard BMI definition (BMI ≥30 kg/m2)
12,829 (30%) were classed as obese when using body fat percentage criteria (≥25% for men or ≥30% women)
Measuring body fat as opposed to BMI is thought to be a more precise (if time-consuming) method of judging whether a person is overweight or obese.
Within the obese participants, 30% were «metabolically healthy» using BMI-based obesity criteria, and 46% were «metabolically healthy» using body fat percentage criteria.
The average follow-up period was said to be 14 years for mortality and eight years for non-fatal cardiovascular disease.
The main findings were:
«Metabolically healthy» obese participants had a better baseline fitness level on the treadmill test compared with «metabolically abnormal» obese participants (adjusting for age, sex, examination year, smoking and alcohol consumption, and when using either BMI or body fat percentage to define obesity). The difference was the same for men and women.
«Metabolically abnormal» obese participants had significantly increased risk of dying from any cause during follow-up compared with «metabolically healthy» obese participants (adjusting for confounders and using either BMI or body fat percentage to define obesity).
When looking at cardiovascular disease outcomes, «metabolically abnormal» obese participants only had increased risk of a fatal or non-fatal cardiovascular disease event compared with «metabolically healthy» obese participants when using body fat percentage to define obesity. There was no difference in risk when using standard BMI definitions.
«Metabolically healthy» obese participants had no difference in risk of dying from any cause, or of fatal or non-fatal cardiovascular disease events compared with «metabolically healthy» normal-weight or fat participants.

How did the researchers interpret the results?

The researchers concluded that metabolically healthy obese individuals have better fitness than their metabolically unhealthy obese counterparts. They also have a better prognosis in terms of mortality and disease risk.

Conclusion

This was an impressive study that benefited from a large sample size, its thorough assessments of medical health and fitness at the study’s start and long duration of follow-up.
It found that metabolic health is a predicator of overall health and fitness in obese people. This does not mean that being obese is healthy.
The study did have a number of limitations:
The one-off measure of fitness on the treadmill is hard to interpret as this was assessed at the same time as obesity and metabolic risk factors. We don’t know how representative this is of the person’s overall fitness in the longer term, which could have varied sharply over time. We also don’t know how long the person has been obese for, which makes it difficult to say much about the fitness of people with obesity, with or without metabolic risk factors.
There are possible issues with the follow-up for mortality and cardiovascular outcomes. The recruitment period was 1979 to 2003, and follow-up terminated in 2003. Although the researchers included only people who had been in the study for at least one year, the follow-up of outcomes may be quite short in some cases. Mortality was reliably monitored via the National Death Index, but non-fatal heart disease was reported only from health surveys in 1982, 1999 and 2004, to which there was only a 65% response rate. This means many cases may have been missed. This reduces the reliability of the measurement of the health outcomes described in the study, compared with an objective measure such as reviewing the medical records of participants.
The researchers also acknowledged that the criteria they used to define «metabolically healthy» and «metabolically unhealthy» may differ from other definitions that could have been used. As they said, they did not include information on waist circumference and did not have information on insulin resistance.
The study included predominantly white, middle-aged men, so it isn’t representative of all population groups.
Overall, the research plausibly suggests that people who are obese but have no other cardiovascular risk factors may be at lower risk of future diseases compared with obese people who have additional cardiovascular risk factors.
However, the research should not be interpreted to mean that being obese is healthy.
A more valid interpretation of these findings, as the authors said, is that it suggests that accurate assessments of body fat percentage and fitness may contribute to the overall assessment of an obese individual.

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Can you really be both ‘fat and fit?’

Escrito por

People «can be obese yet physically healthy and fit and at no greater risk of heart disease or cancer», according to BBC News.
This counterintuitive headline stems from a study that was assessing health outcomes for people who were obese but relatively fit, with only one or no risk factors for «metabolic syndrome». Metabolic syndrome is diagnosed when people have multiple risk factors, such as high blood pressure, that make them more prone to diabetes or cardiovascular disease (CVDs).
Researchers found that the «metabolic healthy» obese group were significantly less likely to develop a CVD or cancer, or die as a result, than people who were similarly obese but were judged to be «metabolic unhealthy». In fact the risks of CVDs and cancers in the «metabolic healthy but obese» group were broadly similar to people with a healthy weight.
However, the research should not be interpreted to mean that being obese is healthy. Waist circumference size is also a risk factor for CVDs, so ideally you should be aiming to have a circumference of less than 94cm (37in) if you’re a man and less than 80cm (31.5in) if you’re a woman.
The research actually tells us very little that is useful in how fitness levels can affect CVD and cancer risk and whether it is possible to be both «fat and fit».
The main implication of the research is that factors other than weight need to be taken in account when assessing these types of health risks.

 

Where did the story come from?

The study was carried out by researchers from the Karolinska Institute, Sweden, the University of Granada, Spain and the University of South Carolina, USA. The research was funded by the National Institutes of Health, the Spanish Ministry of Science and Innovation, the Swedish Heart-Lung Foundation and the Coca-Cola Company (the funding from Coca-Cola was given as an unrestricted grant; in other words «no strings attached»).
The study was published in the peer-reviewed European Heart Journal.

The media reflected the study findings accurately, but the newspaper headlines should not be interpreted to mean that being obese is healthy. A relevant health message that could have been added is that regular exercise can benefit you even if you remain overweight or obese despite your best efforts to lose weight.

What kind of research was this?

This was a cohort study aiming to look at the health of obese individuals who are metabolically healthy and without additional risk factors for CVDs. These were described by the researchers as people with «uncomplicated obesity».
The researchers said that there is uncertainty over the extent to which metabolic health in obese people can influence the risk of CVDs and overall mortality. This is what they aimed to examine.
They decided to examine two theories:
Metabolically healthy but obese individuals have a higher fitness level than obese individuals with metabolic abnormalities.
Metabolically healthy obese people have reduced risk of CVDs, cancer and mortality compared with obese individuals with metabolic abnormalities – the «theoretically unhealthiest group».
In this study, fitness (according to a treadmill test), obesity and metabolic risk factors all appear to have been measured at one point at the start of the study.
But it is difficult to tell how representative this one-off treadmill test is of the overall fitness level of an obese person, particularly as we don’t know how long the person has been obese for.
Measurements on obesity and metabolic health appear to be more reliable than those on fitness.

What did the research involve?

This was an analysis of the Aerobics Center Longitudinal Study (ACLS) which recruited predominantly white professional individuals between 1979 and 2003.
At the time of recruitment a number of assessements were carried out, including:
asking participants to complete a health questionnaire, including medical history and lifestyle habits (such as smoking and alcohol)
a physical examination (including measurement of BMI, body fat percentage and blood pressure) and blood tests taken for fasting blood sugar and lipids (triglycerides and high-density lipoprotein (HDL) «good» cholesterol)
They also performed an exercise treadmill test where they were asked to walk or jog slowly on a treadmill that increases its incline gradually. The test is then ended when the participants feel that they no longer have the stamina to continue (this type of test is known as the Balke treadmill protocol).
A person was defined as metabolically healthy if they met none or only one of the following criteria:
high blood pressure (≥130/85 mmHg)
high blood triglycerides (≥150 mg/dL)
low HDL «good» cholesterol (<40 and 50 mg/dL in men and women, respectively)
high fasting blood sugar level (≥100 mg/dL)
In addition, people with normal blood pressure or fasting blood sugar at the examination, but who reported a history of previously diagnosed high blood pressure or diabetes, were also classed as having these metabolic risk factors.
Participants were followed from recruitment to the end of 2003. Information on mortality came from the National Death Index. Data on non-fatal cardiovascular disease events came from the responses to health surveys in 1982, 1999 and 2004. There was said to be a 65% response rate across surveys.
Eligible participants had no history of cardiovascular disease or cancer at study start (baseline); had complete baseline data on body composition, metabolic risk factors and fitness and completed at least one year of follow-up for health and mortality outcomes.

What were the basic results?

A total 43,265 participants were included in the study (average age 44), a quarter of whom were women.
Of these:
5,649 were obese (13% of the cohort) according to the standard BMI definition (BMI ≥30 kg/m2)
12,829 (30%) were classed as obese when using body fat percentage criteria (≥25% for men or ≥30% women)
Measuring body fat as opposed to BMI is thought to be a more precise (if time-consuming) method of judging whether a person is overweight or obese.
Within the obese participants, 30% were «metabolically healthy» using BMI-based obesity criteria, and 46% were «metabolically healthy» using body fat percentage criteria.
The average follow-up period was said to be 14 years for mortality and eight years for non-fatal cardiovascular disease.
The main findings were:
«Metabolically healthy» obese participants had a better baseline fitness level on the treadmill test compared with «metabolically abnormal» obese participants (adjusting for age, sex, examination year, smoking and alcohol consumption, and when using either BMI or body fat percentage to define obesity). The difference was the same for men and women.
«Metabolically abnormal» obese participants had significantly increased risk of dying from any cause during follow-up compared with «metabolically healthy» obese participants (adjusting for confounders and using either BMI or body fat percentage to define obesity).
When looking at cardiovascular disease outcomes, «metabolically abnormal» obese participants only had increased risk of a fatal or non-fatal cardiovascular disease event compared with «metabolically healthy» obese participants when using body fat percentage to define obesity. There was no difference in risk when using standard BMI definitions.
«Metabolically healthy» obese participants had no difference in risk of dying from any cause, or of fatal or non-fatal cardiovascular disease events compared with «metabolically healthy» normal-weight or fat participants.

How did the researchers interpret the results?

The researchers concluded that metabolically healthy obese individuals have better fitness than their metabolically unhealthy obese counterparts. They also have a better prognosis in terms of mortality and disease risk.

Conclusion

This was an impressive study that benefited from a large sample size, its thorough assessments of medical health and fitness at the study’s start and long duration of follow-up.
It found that metabolic health is a predicator of overall health and fitness in obese people. This does not mean that being obese is healthy.
The study did have a number of limitations:
The one-off measure of fitness on the treadmill is hard to interpret as this was assessed at the same time as obesity and metabolic risk factors. We don’t know how representative this is of the person’s overall fitness in the longer term, which could have varied sharply over time. We also don’t know how long the person has been obese for, which makes it difficult to say much about the fitness of people with obesity, with or without metabolic risk factors.
There are possible issues with the follow-up for mortality and cardiovascular outcomes. The recruitment period was 1979 to 2003, and follow-up terminated in 2003. Although the researchers included only people who had been in the study for at least one year, the follow-up of outcomes may be quite short in some cases. Mortality was reliably monitored via the National Death Index, but non-fatal heart disease was reported only from health surveys in 1982, 1999 and 2004, to which there was only a 65% response rate. This means many cases may have been missed. This reduces the reliability of the measurement of the health outcomes described in the study, compared with an objective measure such as reviewing the medical records of participants.
The researchers also acknowledged that the criteria they used to define «metabolically healthy» and «metabolically unhealthy» may differ from other definitions that could have been used. As they said, they did not include information on waist circumference and did not have information on insulin resistance.
The study included predominantly white, middle-aged men, so it isn’t representative of all population groups.
Overall, the research plausibly suggests that people who are obese but have no other cardiovascular risk factors may be at lower risk of future diseases compared with obese people who have additional cardiovascular risk factors.
However, the research should not be interpreted to mean that being obese is healthy.
A more valid interpretation of these findings, as the authors said, is that it suggests that accurate assessments of body fat percentage and fitness may contribute to the overall assessment of an obese individual.

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