In a recent study, scientists used magnetic resonance imaging (MRI) to map body fat deposits over 18 months in people following two types of diet: Mediterranean/low-carb diets and low-fat diets, with and without moderate physical exercise. The results are published in the journal Circulation.
Diet and exercise are among the most important known lifestyle factors for maintaining good health and a stable weight. However, weight loss isn‘t always a sign of improving health. In fact, the foods we choose can determine where in the body fat is stored, notably around vital organs such as the liver, the pancreas and the heart, as well as around the abdomen.
For equivalent calories and equivalent weight gain, fat isn't deposited in the same places in the body and can indicate metabolic problems, such as visceral fat around the waist, independently of the weight shown on the scale.
This is the subject of a new joint study from Ben-Gurion University of the Negev in Israel, Harvard University in the USA and Leipzig University in Germany. The study mapped the distribution and quantity of specific body fat (adipose) deposits in 278 sedentary adults using MRI, analyzing 300 data points in moderately overweight to obese patients.
Study participants ate either low-fat lunches or a Mediterranean-style lunch low in carbohydrates and saturated fat, plus 28 grams of walnuts, with or without a moderate workout at least three times per week. Calorie count was the same for the two diets.
The results showed that the best strategy for reducing fat deposits around the liver (-29%), the abdomen (-22%) and the heart (-11%) was to combine moderate exercise with a Mediterranean diet, even if weight loss may not be significant. Only fat around the neck and kidneys was not reduced. In fact, this was only altered by weight loss rather than specific lifestyle strategies.
A diet low in fat was found to be less effective in reducing the risk of cardiovascular disease and diabetes associated with fat deposits.
The researchers also found that losing deep subcutaneous fat improved sensitivity to insulin, a hormone secreted by the pancreas that regulates blood sugar levels.
In conclusion, the study authors suggest improving the nutritional quality of diets rather than fixating on the number on the scale.
"We learned in this trial that moderate, but persistent, weight loss may have dramatic beneficial effects on fat deposits related to diabetes and cardiovascular diseases," explains Prof. Iris Shai, one of the lead researchers. "A Mediterranean diet, rich in unsaturated fats and low in carbohydrates, was a more effective strategy than an iso-caloric low-fat diet to dramatically reverse morbid fat storage sites."