There are plenty of diseases for which the risk increases if you are obese. Even if you only carry around a moderate amount of overweight. This is evident based on the extensive statistics study published this week in the New England Journal of Medicine.

The study was funded by the Bill and Melinda Gates Foundation with around 2,300 researchers compiling data from 68.5 million people in 195 countries who have been followed for 25 years.

The results show that obesity is increasing significantly in the world, especially in many poor countries. Burkina Faso, Mali, and Guinea-Bissau are some of the countries where the proportion of obesity has increased the most. In some seventy countries, the proportion of obese people has doubled, including Turkey.

BMI Controvesies

Obesity is usually defined by the BMI (body mass index) method, defined as the body mass divided by the square of the body height, resulting in units of kg/m2. With commonly accepted BMI ranges that are underweight: under 18.5, normal weight: 18.5 to 25, overweight: 25 to 30 and obese: over 30.

Using BMI as a measure of obesity is accompanied by some well-known problems, however, since well-behaved, healthy and muscular people get a relatively high BMI. But even so, when researchers study entire populations, BMI is deemed a useful measure.

Some previous studies have suggested that a BMI just over 25, that is, just above the limit of being overweight, could actually be beneficial to health, at least for people of the upper middle age.

The new study rejects this notion. It shows that what is usually considered normal weight – a BMI of between 20 and 25 – clearly correlates with the lowest risk of disease and premature death.

Smoking distorting results

The fact that some previous studies have seen moderate obesity as beneficial to health may be due to the fact that smoking has clashed with their results, the researcher’s reason. Since smoking – although harmful to health – tend to lower body weight slightly.

This hypothesis appears to be confirmed by this week’s study in The New England Journal of Medicine, based solely, on results from participants who have never smoked. What is usually regarded as normal weight – a BMI between 20 and 25 – clearly correlate with the lowest risk of disease and premature death.

Obesity is peaking

Obesity has peaked in most developed and big countries, but more than every third person has a BMI over 30. The highest proportion of childhood obesity is seen in the United States, where about every eight child is obese. The lowest proportion of obese adults is found in Vietnam, with only a single percentage, and the lowest proportion of obesity among children is seen in Bangladesh, also only a single percentage.

The largest number of obese children, calculated in absolute terms in 2015, was found in China and India. The largest number of obese adults is found in the United States and China.

In our systematic evaluation of the health effects of high BMI, we found that excess body weight accounted for about 4 million deaths and 120 million disability-adjusted life-years worldwide in 2015. Nearly 70% of the deaths that were related to high BMI were due to cardiovascular disease, and more than 60% of those deaths occurred among obese persons. The prevalence of obesity has increased during the past three decades and at a faster pace than the related disease burden. However, both the trend and magnitude of the BMI-related disease burden vary widely across countries.

A paradoxical effect is that in many richer countries, deaths, and diseases associated with obesity have actually decreased in recent years. This is due to the availability of medicines that reduce the risk, such as antihypertensive agents, statins that lower blood fats and drugs that stabilize blood sugar.


Health Effects of Overweight and Obesity in 195 Countries over 25 Years The GBD 2015 Obesity Collaborators June 12, 2017DOI: 10.1056/NEJMoa1614362