Adhering to these traditional concepts the US Department
of Agriculture has concluded that
diets, which reduce calories, will result in effective weight loss independent
of the macronutrient composition, which is considered less important, even irrelevant.14 In contrast with these views, the majority
of ad - libitum studies demonstrate that subjects who follow a low - carbohydrate
diet lose more weight during the first 3 — 6 months compared with those who follow balanced
diets.15, 16, 17 One hypothesis is that the use
of energy from proteins in VLCKD is an «expensive» process for the body and so can lead to a «waste
of calories», and therefore increased weight loss compared with other «less - expensive»
diets.13, 18, 19 The average
human body requires 60 — 65 g
of glucose per day, and during the first phase
of a
diet very low in carbohydrates this is partially (16 %) obtained from glycerol, with the
major part derived via gluconeogenesis from proteins
of either dietary or tissue origin.12 The energy cost
of gluconeogenesis has been confirmed in several studies7 and it has been calculated at ∼ 400 — 600 Kcal / day (due to both endogenous and food source proteins.18 Despite this, there is no direct experimental evidence to support this intriguing hypothesis; on the contrary, a recent study reported that there were no changes in resting energy expenditure after a VLCKD.20 A simpler, perhaps more likely, explanation for improved weight loss is a possible appetite - suppressant action
of ketosis.