New research from Cambridge University suggests that improving diet and increasing physical activity levels may be more effective in preventing weight gain, especially harmful abdominal fat, than simply changing one of these behaviors.

An analysis of changes in physical activity and diet quality among British adults found that while improvements in diet quality and increases in physical activity were independently associated with a reduction in body fat gain, the greatest benefit was obtained by combining both.

Body fat is stored in different locations, some of which are more harmful than others. Subcutaneous fat, stored under the skin, can be considered relatively healthy. In contrast, visceral fat stored around abdominal organs is associated with a higher risk of diseases such as type 2 diabetes, fatty liver, and heart disease.

In a study published today, researchers from the Department of Epidemiology at the Medical Research Council (MRC) at the University of Cambridge, part of the JAMA Network followed 7,256 adults in a Finnish study for seven years.

Researchers also used a food frequency questionnaire to assess participants’ dietary quality by assessing their adherence to the Mediterranean diet pattern. The Mediterranean diet emphasizes fruits, vegetables, whole grains, legumes, nuts, and olive oil, as well as moderate amounts of fish, poultry, eggs, and dairy products, while limiting the consumption of red meat and sweets.

In both studies, researchers also used DEXA to measure the amount and distribution of body fat. DEXA is a low-intensity X-ray scan that can distinguish between fat, bone composition, muscle and lean body mass throughout the body, and used ultrasound to identify the occurrence of fatty liver disease.

Researchers found that, over time, improvements in diet quality and energy expenditure from physical activity were independently associated with reductions or increases in body weight, total body fat, subcutaneous and visceral fat, and a lower incidence of fatty liver disease.

Simultaneous improvement in both diet and physical activity was associated with the greatest reduction in body fat, while improvement in only one of these two behaviors was associated with relatively moderate changes.

Researchers found that after adjusting for body mass index, the association between changes in diet and physical activity and changes in visceral fat remained significant, but the association with subcutaneous fat was not, suggesting that visceral fat is particularly sensitive to changes in health behaviors.

When people talk about weight changes, they usually mean a number on the scale. But not all weight loss or gain is the same. First, when considering the risk of metabolic diseases like diabetes and heart disease, we need to look at the amount of fat. Second, body fat is stored in different places, and some types are more harmful than others. Therefore, it’s important to know where these changes occur when we gain or lose weight.

We have found that combining a better diet with more physical activity is an effective way to not only improve weight but also to improve the amount and location of fat storage in the body. It is particularly effective in reducing the accumulation of harmful fat around organs.

Professor Nita Forouhi, a senior author from the MRC Epidemiology team, stated, “Our research suggests that improving diet and engaging in more physical activity during middle age can not only reduce weight but may also help prevent disease and support a healthier aging process.”

“Despite the challenges of living in an environment that promotes unhealthy eating and lack of activity, there are benefits to making small, consistent changes that can lead to healthier diets and increased energy expenditure.”

“To address the obesity epidemic and its enormous social, psychological, and health service costs, policymakers should seek to change the environment of food and physical activity so that everyone can more easily make healthier choices.”

This research was funded by the Medical Research Council and the Wellcome Trust, and supported by the NIHR Cambridge Biomedical Research Centre.