Scientists at Wake Forest School of Medicine in the US discovered that nonhuman primates who were given a Mediterranean diet chose not to eat all the food available to them and maintained a normal weight.
"By comparison, the animals on a Western diet ate far more than they needed and gained weight," said the study's principal investigator, Carol A. Shively, professor of pathology at Wake Forest School of Medicine.
While the health benefits of the so-called Mediterranean diet are widely acknowledged, the study, published in the journal Obesity, claims to be the first preclinical trial to measure the effects of long-term consumption of a Western versus a Mediterranean diet on obesity-related diseases under controlled experimental conditions. However, a weakness of the study was the modest sample size.
The 38-month study (equivalent to about nine years for humans) prevention trial used 38 middle-aged females that were randomised to either the Mediterranean or Western diet.
The diets were formulated to closely reflect human diets. The Western diet contained protein and fat derived largely from animal sources.
The Mediterranean diet came primarily from plant sources. Both contained comparable proportions of fat, protein and carbohydrates.
Both groups were matched on their baseline weight and body fat and were allowed to eat as much as they wanted throughout the study.
"What we found was that the group on the Mediterranean diet actually ate fewer calories, had lower body weight and had less body fat than those on the Western diet," Shively said.
The Mediterranean diet is at risk of vanishing
The study comes at an important time for the Mediterranean diet, famous for being rich in fruit, vegetables, fish and olive oil. Last year a WHO chief declared the diet has ‘gone’, and has been replaced in the likes of Greece, Spain and Italy by sweets, junk food and sugary drinks.
“The Mediterranean diet for the children in these countries is gone,” said Dr Joao Breda, head of the WHO European office for prevention and control of noncommunicable diseases at the European Congress on Obesity in Vienna.
“There is no Mediterranean diet any more. Those who are close to the Mediterranean diet are the Swedish kids. The Mediterranean diet is gone and we need to recover it.”
The Mediterranean diet can prevent non-alcoholic fatty liver disease
The Mediterranean diet also protected against non-alcoholic fatty liver disease, known as NAFLD, claimed the study. NAFLD can cause cirrhosis of the liver and liver cancer, and require a transplant. Obesity is a major cause of NAFLD. By 2030, one-third of adults in the US are expected to have the disease, and it is the fastest growing reason for liver transplants in young adults in the US.
In Europe, the prevalence of NAFLD in the general population ranges from 20% to 30% and will become the leading cause of liver transplantation in the region in the next 10-20 years, according to the European Liver Patients’ Association.
"Diet composition is a critically important contributor to the US public health, and unfortunately those at the greatest risk for obesity and related costly chronic diseases also have the poorest quality diets," Shively said.
"The Western diet was developed and promoted by companies who want us to eat their food, so they make it hyper-palatable, meaning it hits all our buttons so we overconsume. Eating a Mediterranean diet should allow people to enjoy their food and not overeat.
"We hope our findings will encourage people to eat healthier foods that are also enjoyable, and improve human health."