"You can be fat and healthy," is the misleading headline from the Daily Mail. While a Dutch study did find that activity could help avoid the increased risk of cardiovascular disease associated with obesity, it didn't look at the risks of other obesity-related conditions such as type 2 diabetes and some types of cancer.
The study of 5,344 people aged 55 or over concluded that:
- people who are a healthy weight and do plenty of physical activity had the lowest risk of heart attack or stroke
- people who were overweight or obese, but physically active, had the same risk as people of a healthy weight who exercised regularly
- people at highest risk were those who were obese and did less exercise
It is worth noting that the category researchers used to define "low activity" – an average of two hours of moderate activity a day – was actually more than many people manage in the UK. So the risks of heart disease may actually be higher for people in the UK who are not regularly physically active, whatever their weight.
Another important point is that the study only looked at the risk of cardiovascular disease. Other obesity-related conditions were not considered. And as we have covered previously, 11 types of cancer are now linked to being overweight.
In conclusion, exercise is always beneficial, but if you can make the extra effort to achieve a healthy weight, then the benefits may be enhanced. If you want to lose weight you can try the NHS Weight Loss Plan.
Where did the story come from?
The study was carried out by researchers from Erasmus University Medical Centre in the Netherlands and was funded by Erasmus University, the Netherlands Organisation for Scientific Research, the Netherlands Organisation for Health Research and Development, the Research Institute for Diseases in the Elderly, the Ministry of Education, Culture and Science, the Ministry for Health, Welfare and Sports, the European Commission and the municipality of Rotterdam.
Although several of the researchers work for a research centre funded by Nestlé, there does not seem to be a conflict of interest. The study was published in the peer-reviewed European Journal of Preventative Cardiology.
The Daily Mail's headline that "You can be fat and healthy" is misleading as the study looked only at cardiovascular disease. Being overweight or obese also affects the chances of other conditions, including cancer and diabetes.
And this came only a day after the same newspaper reported "How being obese can increase the risk of developing 11 types of cancer including breast, stomach and bowel", so you could forgive their readers for being more than a little confused.
Also, the study's authors specifically say their results do not refute the cardiovascular risk associated with overweight and obesity.
What kind of research was this?
This was a prospective cohort study which followed up groups of adults aged 55 and over for an average of 10 years.
This type of study is useful for spotting patterns and links between factors such as body weight, activity levels, and the development of disease over time. But it cannot prove that one factor causes another.
What did the research involve?
Researchers interviewed and measured 6,510 people aged 55 or above in Rotterdam, in two phases (1990 to 1993 and 2000 to 2001). They were asked about their activity levels and diet, using a questionnaire. Researchers recorded their body mass index (BMI).
They then followed up what happened to people over the following years.
They analysed the figures to see whether people who were overweight or obese were more likely to have a heart attack or stroke during follow up, and how their reported levels of physical activity affected this risk.
Researchers excluded people who already had cardiovascular disease, had important missing data, or who were underweight. They were left with 5,344 people to include in the analysis.
Physical activity was defined as high or low, based on whether they did more or less than the average amount of moderate physical activity reported by people in the study.
Average amounts of activity in the high group were four hours a day, while average amounts in the low group were two hours a day.
Moderate physical activity is activity that raises your heart rate and makes you a little out of breath, such as brisk walking.
The researchers took account of the following potentially confounding factors:
- alcohol use
- education level
- dietary information (although this was missing for almost a quarter of participants)
- family history of early heart attack
What were the basic results?
People who were obese or overweight did not have an overall increased risk of heart attack or stroke compared to people of a healthy weight, above that which might have been caused by chance. However, when the researchers took account of physical activity levels, patterns emerged.
Compared to people of normal weight with high activity levels:
- People who were overweight with low physical activity levels had a 33% higher risk of a heart attack or stroke (hazard ratio [HR] 1.33, 95% confidence interval [CI] 1.07 to 1.66).
- People who were obese with low physical activity levels had a 35% higher risk of heart attack or stroke (HR 1.35, 95% CI 1.04 to 1.75).
- People with low physical activity levels were at higher risk of heart attack or stroke, compared to people with high activity levels, regardless of how much they weighed (HR 1.22, 95% CI 1.06 to 1.41).
How did the researchers interpret the results?
The researchers said: "Our findings suggest that the beneficial impact of physical activity on CVD [cardiovascular disease, including heart attack or stroke] might outweigh the negative impact of body mass index among middle-aged and elderly people." They say this "emphasises the importance" of physical activity for everyone, at all ages.
However, they don't say that being overweight has no health consequences. They say that being very physically active might offset the known cardiovascular risk associated with being overweight.
As people often say, if exercise was a medicine, it would be hailed as a miracle cure. This study suggests that what we already know about the benefits of exercise may extend to reducing risk of cardiovascular disease for middle aged and older people, even if they are overweight or obese.
But the study has some limitations. This type of study can't prove that one factor – exercise – is responsible for the lower risk of heart attack and stroke among overweight or obese people who exercise more. It's possible that other factors are important – for example people's income may be linked to their opportunities for exercise.
In addition, people are more likely to be physically active when they are in good health, so lower levels of physical activity might suggest people are already unhealthy, and therefore more at risk of heart attack or stroke.
The amounts of exercise people reported are strikingly high. The study didn't measure activity through monitoring devices, so we can't be sure that people didn't overstate how much activity they were doing.
The study included physical activity for transport as well as leisure, so one possibility is that people in Rotterdam get around on foot or bicycle a lot (a factor that may be more significant in the Netherlands than the UK).
So the differences in activity levels from the usual levels reported in the UK mean that the results may not translate to a UK population. Latest figures show only 67% of men and 55% of women in England meet guidelines to do half an hour, five days a week, of moderate physical activity.
While physical exercise is certainly a good thing, we can't be sure that it completely negates the importance of keeping to a healthy weight. Obesity increases the chances of diabetes, cancer and other diseases, as well as cardiovascular disease.
Read more about the benefits of exercise.