Not always harmful to health to be fat

16/06/06 The conventional wisdom says that it is always harmful to your health to be overweight, and all obese and overweight people should try to lose weight. But this is not the case, as is shown in two new dissertations from Lund University in Sweden.

Obesity in combination with risk factors like diabetes, high blood pressure, high blood lipids, and smoking do indeed increase the risk of cardiovascular diseases, but being fat in itself poses no significant risk. And for overweight patients who have already suffered a heart attack, losing weight can even be dangerous.

The latter finding is presented in a dissertation by Linn Kennedy.

She studied more than 12,000 patients after myocardial infarction and compared developments in their weight and health. The results were unexpected: those who lost weight had a lower survival rate, while those who gained weight were none the worse for it, even if they were already overweight from the start.

“European recommendations state that overweight patients after myocardial infarction should be recommended to lose weight. But the recommendations are not based on any studies, because our study is in fact the first in the field. And it unfortunately indicates that medical science may have shortened the lives of a number of overweight patients with myocardial infarction by persuading them to diet!” says Linn Kennedy’s thesis director, Ronnie Willenheimer.

He now urges his patients who have had a myocardial infarction to eat healthful foods and exercise, but not to pay any attention to the numbers on the scales. And he also maintains that inexplicable weight loss in a patient after myocardial infarction should not be welcomed with joy: it might mean that the patient is sicker than was previously thought.

The fact that obesity does not seem to be harmful to patients after myocardial infarction may be due to the fact that it provides the body with more reserves for its metabolism. Modern drug treatment after a myocardial infarction may also play a role, since it seems to protect against the negative effects on health that obesity otherwise might entail.

The other dissertation on the theme of obesity was written by Susanna Calling. She used two large groups of more than 22,000 and more than 28,000 individuals respectively, individuals who were part of two major population studies in the city of Malmö.

By comparing their data with other registers, she was able to see which individuals later contracted cardiovascular diseases or died young.

In one of the studies Susanna Calling examined obesity as a risk factor for myocardial infarction and death. Obesity proved to be such a risk factor, but above all in combination with other risk factors like diabetes, high blood pressure, high blood lipids, and not least smoking. Fully 16 percent of the obese individuals had none of these risk factors, and for them the risk of having a myocardial infarction was not heightened.

The second study deals with obesity in combination with various occupations and marital status. The study shows that obesity, discounting other risk factors, increased the risk of myocardial infarction only for single men in the working class or in self-employment. Just living alone entailed a considerably heightened myocardial infarction risk for overweight men.

“My conclusion is that overweight people should not be seen as a homogeneous group. Obesity is a health risk for many people, but in no way for everybody. If you wish to lower the risk of people having myocardial infarction, you should therefore concentrate on the most vulnerable groups and not attempt to get all overweight people to lose weight,” says Susanna Calling.