‘Your scale isn’t giving you the whole picture’
Different types of fat deposits in your body are impacted differently by diet and exercise, says a new, long-term diet study published by researchers at Ben-Gurion University of the Negev in the journal Circulation of the American Heart Association.
“These 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,” said the study’s primary investigator leader, Prof. Iris Shai of BGU.
“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,” Shai explained. Thus, a Mediterranean diet, rich in unsaturated fats and low in carbohydrates, was a more effective strategy than a low-fat diet with similar amounts of calories to dramatically reverse morbid fat storage sites.
The Beersheba team used MRI imaging technology for the first time to plot the diverse changes in an array of body-organ fat storage pools during 18 months of Mediterranean/low-carbohydrate (Med/LC) and low-fat diets, with and without moderate physical exercise.
Called the “Central MRI study,” it was a randomized, controlled trial conducted at BGU in collaboration with the Dimona Nuclear Research Center and Soroka University Medical Center, along with Harvard University in Cambridge and Leipzig University in Germany. The research group, led by Shai, Dr. Yiftach Gepner, Dr. Ilan Shelef, and Dr. Dan Schwarzfuchs from BGU, as well as Dr. Meir Stampfer from Harvard, sought to assess how lifestyle strategies would impact specific body (adipose) fat deposits.
To map these deposits, they collected an unprecedented quantity of whole body MRI data in benchmark six-month and 18-month scans, each with 300 data points, 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 of how different fat deposits are impacted disproportionately by diet and exercise,” said Shai.
The study found that even with only moderate weight loss, the Med/LC diet was significantly more effective than a low-fat diet in decreasing some of the fat storage pools, including visceral (abdominal deep), intra-hepatic (liver), intra-pericardial (heart), and pancreatic fats. However, fat deposits in renal-sinus (kidney), femoral-intermuscular or the cervical (neck) were changed only by losing weight and not by specific lifestyle changes such as exercise.
The various fat deposits exhibited highly diverse responsiveness to the interventions, along with moderate, long-term weight loss. In general, the greatest fat deposit decreases were around the liver (-29%), abdominal-deep (-22%) and heart (-11%). Pancreatic and femur intermuscular fat deposits, on the other hand, were only reduced by 1-2%.
The 18-month trial included 278 sedentary adults in an isolated workplace, the Nuclear Research Center, with a monitored lunch provided. The participants were randomized to a low-fat or Med/ LC diet of similar amounts of calories, plus 28 grams of walnuts per day with or without an added moderate workout at least three times weekly and a supervised, free gym membership.
The researchers wanted to know whether internal bodyfat redistribution, rather than mild weight loss, underscored the significant health benefits attributed to Med/LC diets.
The researchers found that the decline in hepatic fat and each one of the abdominal fat deposits had specific related health outcomes. After controlling for several parameters, losing visceral fat or hepatic fat were discovered to be independently associated with an improved lipid profile, losing deep fat under the skin was associated with improved insulin sensitivity, and losing superficial subcutaneous fat remained neutral, except for association with a decrease in the leptin hormone.
In conclusion, the “Central MRI study” demonstrates that improving nutritional quality and being physically active can improve cardio-metabolic risk markers through changes in fat deposits in the abdomen and surrounding internal organs “that are not reflected by changes in body weight alone,” Shai concluded.