One of the most researched diets to date is the Mediterranean diet. This diet has been shown to have a variety of benefits. But could it be more effective for weight loss when combined with another well-studied approach – semi-fasting?
Daily calorie restriction is the standard way to lose weight. But more research is suggesting that intermittent restriction may be a viable alternative. This type of ‘semi-fasting’ consists of feed days, with ad libitum intake, and fast days, which restricts down to 20-25% of energy needs. It may even confer additional metabolic benefits, further supporting weight loss efforts.
People who are overweight or obese are at risk of many chronic diseases, including type 2 diabetes, heart disease and cancer. But a Mediterranean diet has been found to reduce many risk factors associated with these chronic diseases. Combining the weight-loss benefits of intermittent fasting and health benefits of a Mediterranean approach may be particularly effective.
A 6-week randomised controlled trial exploring the effects of a Mediterranean diet with or without a semi-fast on weight loss. 50 participants were randomised into two groups. One group undertook a Mediterranean Diet with a 5-day semi-fast group, and the other a hypocaloric Mediterranean Diet group (500kcal deficit). A total of 42 participants were included in the final analysis.
Participants were aged between 30-65 and classified as overweight or obese. Exclusion criteria included chronic disease such as autoimmune disease, cancer, hepatitis and eating disorders, as well as bariatric surgery.
The Mediterranean Diet guidelines included recommendations of using olive oil, consuming 2 serves of vegetables per day, 2-3 servings of fruit daily, 3 serves of legumes per week, 3 serves of fish or shellfish per week, 1 serve of nuts or seeds per week, choosing white meat over red or processed meat, and using tomato, garlic and onion regularly when cooking.
It was advised to limit or remove cream, butter, margarine, processed meats, sugar, baked goods, desserts and chips. Participants who drank alcohol regularly were advised to use wine as their drink of preference, consuming max 300ml/day. Those who were not regular drinkers were advised to have one glass of wine (100-150ml) per day.
For those in the semi-fast group, 5 days of the trial were set with a limit of 600-700kcal, with 3 serves of juice, one serve of puree and one serve of gazpacho each day. Ingredients for these were provided to participants. Additionally, two days of adaptation and two days of exit were included to help participants adapt to the semi-fast.
During baseline and follow-up, a number of anthropometric measurements including weight, BMI body fat mass, visceral fat, muscle mass and waist circumference were assessed and recorded. Diet was assessed before the trial and monitored throughout. Participants were also supervised for 3 weeks to ensure adherence to treatment.
Both groups saw similar changes in anthropometric measurements at the conclusion of the trial. Those in the semi-fast group lost 4.8% of their baseline weight and 7.3% fat mass. Those in the hypocaloric diet group lost 3.5% weight and 8.5% fat mass. Both groups lost a similar amount of visceral fat mass – 11.5% for the semi-fast, and 11.9% for the hypocaloric diet.
The researchers concluded that semi-fasting is a viable alternative to daily caloric restriction when it comes to weight loss. However, they did note that the trial was short and had a small sample size. They also suggested that there may have been a greater benefit if dietary counselling was available after the trial to aid in maintenance of the new dietary approach.
Therefore, further studies are needed to explore whether semi-fasting is superior in terms of body composition and weight, and if it is safe and sustainable.
Jimenez, A.M., Oliva, S.L., Vilar, E.G., de Cuevillas, B., Morais Moreno, M.D.C., Gabella de Prado, J., Diaz, E.A., Martin, M. and San, I., The Mediterranean diet pattern with intermittent semi-fasting may facilitate weight loss: randomised controlled trial. Mediterranean Journal of Nutrition and Metabolism, (Preprint), pp.1-9.