A new, long-term diet study published in the American Heart Association journal, Circulation, used MRI imaging technology for the first time to plot the changes in an array of body organ fat storage pools during 18 months of Mediterranean/low-carb (Med/LC) and low-fat diets, with and without moderate physical exercise.
This randomized, controlled trial conducted sought to assess how distinct lifestyle strategies would impact specific body (adipose) fat deposits.
To map these deposits, they collected whole body MRI data in six-month and 18-month scans from moderately overweight to obese men and women.
"Weighing patients or using blood tests to detect changes, hasn't, until now, given us accurate pictures, literally, of how different fat deposits are impacted disproportionately by diet and exercise," the researchers said. The findings suggest that moderate exercise combined with a Mediterranean/low carb diet may help reduce the amount of some fat deposits even if you don't lose significant weight as part of the effort.
Low carb, Mediterranean diet outperformed low fat diet
In the study, even with only moderate weight loss, the Med/LC diet was found to be significantly superior to a low-fat diet in decreasing some of the fat storage pools, including visceral (deep abdominal) fat and fat in the liver, heart and pancreas. However, fat deposits in the kidney, muscle and neck were only altered by losing weight and not by specific lifestyle strategies.
In general, the greatest fat deposit decreases were liver (-29 percent), visceral (-22 percent) and around the heart (-11 percent).
The findings suggest that moderate, but persistent, weight loss may have dramatic beneficial effects on fat deposits related to diabetes and cardiovascular diseases. A Mediterranean diet, rich in unsaturated fats and low in carbohydrates, was a more effective strategy than a low-fat diet to reduce fat storage.
The 18-month trial included 278 sedentary adults with a monitored lunch provided. The participants were randomized to low-fat or Med/LC diet+28 grams of walnuts per day with or without an added moderate workout at least three times weekly and a supervised, free gym membership. Both diets provided a similar number of calories.
Two previous studies found that Med/LC diets were effective in improving the cardio-metabolic health and in reversing atherosclerosis in the carotid arteries. Based on those findings, the researchers asked whether internal body fat redistribution, rather than mild weight loss differences between the diets, may underline the significant health benefits attributed to Med/LC diets.
The researchers also found that losing visceral fat or liver fat were independently associated with improved blood fats. Losing deep visceral fat was associated with improved insulin sensitivity.
The findings demonstrate that improving nutritional quality of the diet and being physically active can improve cardio-metabolic risk markers through changes in fat deposits that are not reflected by changes in body weight alone.
Source: Circulation, November 15, 2017.
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