The role of dietary protein in weight loss and weight maintenance encompasses influences on crucial targets for body weight regulation, namely satiety, thermogenesis, energy efficiency, and body composition. Protein-induced satiety may be mainly due to oxidation of amino acids fed in excess, especially in diets with “incomplete” proteins. Protein-induced energy expenditure may be due to protein and urea synthesis and to gluconeogenesis; “complete” proteins having all essential amino acids show larger increases in energy expenditure than do lower-quality proteins. With respect to adverse effects, no protein-induced effects are observed on net bone balance or on calcium balance in young adults and elderly persons. Dietary protein even increases bone mineral mass and reduces incidence of osteoporotic fracture. During weight loss, nitrogen intake positively affects calcium balance and consequent preservation of bone mineral content. Sulphur-containing amino acids cause a blood pressure–raising effect by loss of nephron mass. Subjects with obesity, metabolic syndrome, and type 2 diabetes are particularly susceptible groups. This review provides an overview of how sustaining absolute protein intake affects metabolic targets for weight loss and weight maintenance during negative energy balance, i.e., sustaining satiety and energy expenditure and sparing fat-free mass, resulting in energy inefficiency. However, the long-term relationship between net protein synthesis and sparing fat-free mass remains to be elucidated.

The present study was conducted to investigate whether green tea may improve weight maintenance by preventing or limiting weight regain after weight loss of 5 to 10% in overweight and moderately obese subjects. The study had a randomised, parallel, placebo-controlled design. A total of 104 overweight and moderately obese male and female subjects (age 18–60 years; BMI 25–35kg/m²) participated. The study consisted of a very-low-energy diet intervention (VLED; 2·1MJ/d) of 4 weeks followed by a weight-maintenance period of 13 weeks in which the subjects received green tea or placebo. The green tea contained caffeine (104mg/d) and catechins (573mg/d, of which 323mg was epigallocatechin gallate). Subjects lost 6·4 (sd 1·9) kg or 7·5 (sd 2·2) % of their original body weight during the VLED (P<0·001). Body-weight regain was not significantly different between the green tea and the placebo group (30·5 (sd 61·8) % and 19·7 (sd 56·9)%, respectively). In the green tea treatment, habitual high caffeine consumption was associated with a higher weight regain compared with habitual low caffeine consumption (39 (sd 17) and 16 (sd 11)%, respectively; P<0·05). We conclude that weight maintenance after 7·5% body-weight loss was not affected by green tea treatment and that habitual caffeine consumption affected weight maintenance in the green tea treatment.

We hypothesized that progressive loss of body mass during high-altitude sojourns is largely caused by decreased food intake, possibly due to hypobaric hypoxia. Therefore we assessed the effect of long-term hypobaric hypoxia per se on appetite in eight men who were exposed to a 31-day simulated stay at several altitudes up to the peak of Mt. Everest (8,848 m). Palatable food was provided ad libitum, and stresses such as cold exposure and exercise were avoided. At each altitude, body mass, energy, and macronutrient intake were measured; attitude toward eating and appetite profiles during and between meals were assessed by using questionnaires. Body mass reduction of an average of 5 ± 2 kg was mainly due to a reduction in energy intake of 4.2 ± 2 MJ/day (P < 0.01). At 5,000- and 6,000-m altitudes, subjects had hardly any acute mountain sickness symptoms and meal size reductions (P < 0.01) were related to a more rapid increase in satiety (P < 0.01). Meal frequency was increased from 4 ± 1 to 7 ± 1 eating occasions per day (P < 0.01). At 7,000 m, when acute mountain sickness symptoms were present, uncoupling between hunger and desire to eat occurred and prevented a food intake necessary to meet energy balance requirements. On recovery, body mass was restored up to 63% after 4 days; this suggests physiological fluid retention with the return to sea level. We conclude that exposure to hypobaric hypoxia per se appears to be associated with a change in the attitude toward eating and with a decreased appetite and food intake.