Low energetic diets can achieve short-term weight loss, but often the slimming process is not sustainable in the long term [13].
The traditional nutritionally adequate low energy diets frequently failed to promote stable weight losses, and the explanations for such limited success were mostly the "poor adherence" to specific low-energy diets.
A study about the effect of energy restriction and diet composition on weight loss and changes in plasma lipids and glucose levels concluded that all energy-restricted diets improve glucose control independently of diet composition, while only the lipoprotein profile was affected by the macronutrient composition [14].
Recently, diets low in carbohydrate (low- carbohydrate diets) have become the focus of international attention since the recent WHO recommendations to reduce the overall consumptions of sugars and some health professionals recommendations to reduce the consumption of rapidly digestible starches that lead to high glucose responses [15].
A study about the influence of low-carbohydrate or low-fat diet on weight loss and risk factors for atherosclerosis in the elderly, obese patients with type 2 diabetes mellitus, shows that the results were more obvious in patients with carbohydrate-restricted diet, with a relative improvement in insulin sensitivity and triglycerides levels [12].
High protein low-carbohydrate diets have been proposed as an alternative to conventional diets, in order to reduce or treat the risk of obesity, CVD and type 2 diabetes mellitus [16].
But this carbohydrate restriction produces a depletion of glycogen stores leading to excretion of bound water, and ketogenic effect.
It has been proposed that the glycaemic index of foods can influence body-weight control [17]. Short-term studies suggest that low-glycaemic index carbohydrates and fiber intake could delay hunger and decrease subsequent energy intake compared with high-glycaemic index foods [18].
The glycaemic index (GI) is defined as "the incremental area under the blood glucose curve following ingestion of a test food, expressed as a percentage of the corresponding area following an equivalent load of a reference carbohydrate, either glucose or white-wheat bread"[19,20].
The GI of a food will vary depending on the rate of digestion. The faster the digestion of a food, the higher is the GI value (>70).
Also, the GI is defined as Food with a low GI (≤ 70) are considered to be favorable in terms of health, particularly for the prevention of obesity, T2DM, and CVD. The GI is affected by a number of factors:
1 the type of carbohydrate (glucose, 138; maltose, 105; saccharose, 75; fructose, 30);
2 the fat and protein content of food (a lower GI is associated with a slowing of gastric emptying);
3 acidity affects gastric emptying and hence the GI a food, the addition of citric acid or other fruits will therefore lower the GI;
4 the physical properties of food (i.e., water content);
5 the presence of viscous soluble fibers; ripeness, cooking, or processing that renders the carbohydrate more digestible (e.g., starch) will increase the GI;
6 the presence of other factors (i.e., insoluble fiber as found in whole intact grains) that slow absorption of the carbohydrate.
After consumption of high GI foods, there is a large, rapid rise in the level of blood glucose, a large insulin response, and glucagons release is strongly inhibited. Low-GI foods may also delay the return of hunger, by slowing gastric emptying. Many low-GI foods are high in fiber content, which prolongs the distension of the gastrointestinal tract, causing increased and prolonged secretion of the gut peptides cholecystokinin, ghrelin, glucagons, glucagons-like-peptid-1, and glucose-dependent insulinotropic polypeptide, all of which have been suggested as potential satiety factors [21,22].