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Watch: You should try the Mediterranean diet version of tuna salad
01:43 - Source: CNN
CNN  — 

Older people who followed a lower-calorie Mediterranean diet and minimally exercised up to six days a week gained muscle and lost a significant amount of body fat by the end of a year and kept much of it off for three years, according to a new study.

“This study demonstrates that a calorie-controlled Mediterranean diet plus exercise does not simply produce weight loss; it results in a redistribution of body composition from fat to muscle,” said Dr. David Katz, a specialist in preventive and lifestyle medicine, who was not involved in the study.

In addition to a loss of overall body fat, participants in the study lost dangerous visceral belly fat, which could lead to diabetes, heart disease and stroke.

While the findings of the new study are “no surprise,” they extend the benefits of diet and exercise “from mere weight loss to the mobilization of harmful, visceral fat,” said Katz, president and founder of the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine.

Visceral fat cannot be seen. It lies behind stomach muscles, surrounding organs deep within the abdomen. If visceral fat is about 10% of your body’s total fat mass, that’s normal and healthy, according to the Cleveland Clinic. Too much visceral fat, however, can create inflammation, contributing to chronic disease.

“This study confirms that we can profoundly change our metabolic status,” said leading nutrition researcher Dr. Walter Willett, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health and professor of medicine at Harvard Medical School in Boston.

“We now need to provide a supportive environment and resources to help people make this shift because this will benefit both individuals and society as a whole,” said Willett, who was not involved in the study.

Part of a longer study

The research is part of an eight-year randomized clinical trial in Spain, with 23 research centers testing how diet and exercise can reduce cardiovascular risk in men and women between the ages of 55 and 75. All of the 6,874 participants in the trial were overweight or obese and had metabolic syndrome — high blood pressure, high blood sugar, altered cholesterol and excess fat around the waist.

The new study, published Wednesday in the journal JAMA Network Open, examined one- and three-year results in a subpopulation of 1,521 people who underwent scans to determine levels of visceral abdominal fat.

A lower-calorie Mediterranean diet could include proteins such as salmon, chicken breast and tuna, as well as fruits, vegetables, nuts, seeds, legumes and olive oil.

Half of the group was asked to follow a Mediterranean diet wi