The large-scale random study called Diogenes involved a total of 772 European families, comprising 938 adult family members and 827 children. The overweight adults with a mean body mass index (BMI) of 34 kg/sq m initially followed a low-calorie diet (800 kcal/day) for eight weeks, losing an average of 11 kg.
They were then randomly assigned to one of five different low-fat diet types which they followed for six months in order to test which diet was most effective at preventing weight regain:
- A low-protein diet (13% of energy consumed) with a high glycemic index (GI)*
- A low-protein, low-GI diet
- A high-protein (25% of energy consumed), low-GI diet
- A high-protein, high-GI diet
- A control group which followed the current dietary recommendations without special instructions regarding glycemic index levels
A high-protein, low-GI diet works best
It was found that those who followed a maintenance diet high in protein and low in refined carbohydrates were the least likely to regain any weight, and were also the least likely to drop out of the study.
The Diogenes study also concludes that the current dietary recommendations are not optimal for preventing weight gain among overweight people.
The children's study
Meanwhile the 827 children in the families were never required to go on a diet or count calories - they simply followed the same diet as their parents. Around 45% of the children were overweight at the start of the study.
The results were remarkable - in the group of children who maintained a high-protein, low-GI diet the prevalence of overweight dropped spontaneously by around 15%.
About glycemic index
The glycemic index (GI) measures the effects of carbohydrates on blood sugar levels. Carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream have a high GI, while carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, have a low GI. Low GI foods keep us fuller for longer, making them a good choice for people trying to lose weight.
Drastic increases in blood glucose levels give rise to several potentially undesirable effects that can influence the body's metabolism as well as our ability to perform mentally. It is therefore most appropriate to maintain a diet that results in slow digestion and thus more stable blood glucose levels and greater satiety.
A diet with a high protein content contains many protein-rich foods such as lean meat, poultry, fish, eggs and low-fat dairy products. Legumes also contain high levels of protein, as do nuts and almonds. Proteins are significantly more filling than both carbohydrates and fat.
Special requirements for a low-glycemic diet
The glycemic index applies to carbohydrate-containing foods. The recommendations are that some types of fruit may be consumed ad libitum, such as apples, pears, oranges, raspberries and strawberries. Other types should be eaten in only very limited amounts, including bananas (especially overripe bananas), grapes, kiwi, pineapple and melon. Nearly all vegetables are permitted, with the exception of corn, which should be limited. Carrots, beets and parsnip should preferably be eaten raw.
With regard to cereal-based foods (bread, grain, corn, hulled grains and breakfast products), the goal is to eat as many coarse and wholegrain foods as possible, i.e. wholegrain breads with many kernels, wholegrain pasta, whole oats and the special varieties of wholegrain cornflakes
Potatoes should be cooked as little as possible. Try to stick to new potatoes, and it is a good idea to eat them cold. Avoid mashed potatoes and baked potatoes.
Pasta should be cooked al dente and is best eaten cold.
Choose rice varieties such as brown rice, parboiled rice or basmati.
White bread without kernels, white rice and sugary breakfast products should be avoided. In general, sugar intake should be limited, not so much because of its GI but to avoid all those 'empty calories'.
Example of a day's menu for a high-protein, low-GI diet
The study authors said a typical high-protein, low-GI diet meal plan would be:
Breakfast of natural, unflavored yogurt low in fat and fairly high in protein, with muesli, whole-grain crisp bread with low-fat cheese and an orange.
Vegetable sticks and low-fat cheese sticks for a snack.
Lunch of whole-grain rye bread with lean meat or chicken cold cuts, mackerel in tomato sauce and vegetables
Whole-grain rye bread with low-fat liver pate and cucumber for a snack.
Dinner of stir-fried turkey with vegetable and whole-grain pasta; avocado salad with feta cheese and sugar peas.
It is best to drink water or low-fat milk with meals.
- Thomas Meinert Larsen, Stine-Mathilde Dalskov, Marleen van Baak, Susan A. Jebb, Angeliki Papadaki, Andreas F.H. Pfeiffer, J. Alfredo Martinez, Teodora Handjieva-Darlenska, Marie Kunešová, Mats Pihlsgård, Steen Stender, Claus Holst, Wim H.M. Saris, Arne Astrup. Diets with High or Low Protein Content and Glycemic Index for Weight-Loss Maintenance. New England Journal of Medicine, 2010; 363 (22): 2102
- A. Papadaki, M. Linardakis, T. M. Larsen, M. A. van Baak, A. K. Lindroos, A. F. H. Pfeiffer, J. A. Martinez, T. Handjieva-Darlenska, M. Kunesova, C. Holst, A. Astrup, W. H. M. Saris, A. Kafatos. The Effect of Protein and Glycemic Index on Children's Body Composition: The DiOGenes Randomized Study. Pediatrics, 2010; 126 (5): e1143
- The Diogenes (Diet, Obesity and Genes) Project.
- A Glycaemic Food Chart