The unique merits of a low-fat diet for weight control

Impact of carbohydrate and fat intake on weight-reducing efficacy of orlistat

BACKGROUND

Orlistat treatment of obesity results in a poor long-term weight loss (< 5%) in about 30% of patients.

AIM

Total energy and macronutrient intake were examined to assess the effect of a change in eating habits on weight loss.

METHODS

Sixty-two patients consumed a hypocaloric diet, together with orlistat (3 x 120 mg/day), for 72 weeks, with a maximal fat allowance of 30% of the energy intake. At regular intervals, food diaries were recorded.

RESULTS

Fifty-six patients completed the study and lost 8.5 +/- 0.88 kg (P < 0.001). Energy intake was approximately 1500 kcal/day during the entire study period. In three sub-groups established according to weight loss (1, < 5%; 2, > 5% and < 10%; 3, > 10%), fat intake was within the recommended range in all groups during the first 6 months, but thereafter only in group 3. All groups increased their carbohydrate consumption, with the greatest increase in group 1, which could account for the rapid regain of initially lost body weight in this group.

CONCLUSION

At the beginning of a weight management programme in conjunction with orlistat, a low fat intake is advised for an efficient reduction in body weight. Subsequently, in patients with poor long-term weight loss, dietary recommendations must also consider carbohydrate restriction to ensure an adequate hypocaloric diet.

Low-energy substitutes for sugars and fats in the human diet: impact on nutritional regulation

Low-calorie substitutes for dietary sugars and fats are offered to the public as aids in the control of body weight. Their actual influence on food intake and energy regulation has been studied in many acute and longer-term studies. Artificial sweeteners are often presented as preloads, and their effects on subsequent intake are compared to those of sugars or nonsweet vehicles. Preloads are often liquid (drinks) or semisolid (yogurts) and presented as snacks, rather than parts of a meal. Under these conditions, partial or complete compensation for the missing energy is observed most often over the course of a few hours. However, increases in appetite have also been reported. Low-energy fat substitutes also apparently allow energy, but not nutrient (fat) compensation. Short-term, medium-term, and long-term behavioural responses to the use of low-energy substitutes can be different, mainly as a result of learning. Consequently, effects of their chronic use on body weight, body composition, nutritional balance, and various physical parameters are only partially predictable on the basis of present knowledge. The present article reviews recent contributions to this field and delineate open areas of research.

Promotion of hepatic lipid oxidation and gluconeogenesis as a strategy for appetite control

There is considerable evidence that hepatic vagal afferents monitor the availability of liver glycogen and glucose metabolites, and that this mechanism participates in appetite regulation. Thus, promotion of gluconeogenesis and liver glycogen storage may enhance satiety. Hepatic lipid oxidation drives gluconeogenesis by positive allosteric modulation of pyruvate carboxylase and fructodiphosphatase. The rate-limiting enzyme for hepatic lipid oxidation, carnitine acyltransferase I, is activated by exogenous carnitine, and inhibited by malonyl coA. The lipogenesis inhibitor (-)-hydroxycitrate--a natural fruit acid found in the Brindall berry--can decrease production of malonyl coA in hepatocytes by potent inhibition of citrate lyase; many studies demonstrate that (-)-hydroxycitrate can reduce body fat accumulation in growing rats, owing in large part to a reduction in appetite. Joint administration of (-)-hydroxycitrate and carnitine should therefore promote hepatic lipid oxidation, gluconeogenesis, and satiety. Thermogenic effects as well as a reduction of the respiratory quotient can also be predicted. If this technique proves clinically useful in weight management, it could be used in conjunction with chromium picolinate and soluble fiber supplements, which appear to aid hunger control at the level of the hypothalamus and terminal ileum, respectively.

Insulin resistance in Mexican Americans--a precursor to obesity and diabetes?

Mexican Americans appear to have a strong genetic predisposition to insulin resistance, android obesity, and type II diabetes, apparently as a function of Native American genetic heritage. Theoretical considerations suggest that insulin resistance may be a primary factor that plays a causative role in the induction of both obesity and diabetes. Measures which promote optimal insulin sensitivity--chromium picolinate, brewer's yeast, soluble fiber supplements, metformin, very-low-fat diet, exercise training--may have value for preventing, treating, or retarding the onset of obesity and diabetes, and merit clinical evaluation in this regard. Correction of insulin resistance may also lessen cardiovascular risk, in part by reducing LDL cholesterol and improving risk factors associated with Syndrome X. These comments are likely to be valid for other Native American groups at high risk for diabetes.