The role of dietary fat in the prevention and treatment of obesity. Efficacy and safety of low-fat diets

Abstract

BACKGROUND: Does dietary fat play a central role in weight gain and development of obesity? Do low-fat diets have adverse effects on blood lipids? OBJECTIVE AND DESIGN: To answer these questions we have reviewed the evidence linking the dietary fat content to energy balance and obesity, and examined the efficacy and safety of ad libitum low fat, high carbohydrate=protein diets in the prevention and management of obesity. RESULTS: Physiological studies have provided insight into the mechanisms by which the macronutrients differ in their effect on energy balance: (1) energy from fat is less satiating than energy from carbohydrate, and a high fat=carbohydrate ratio in the diet promotes passive overconsumption, a positive energy balance and weight gain in susceptible individuals; (2) fat is more readily absorbed from the intestine and fecal energy loss is much lower with a high dietary fat=carbohydrate ratio; (3) carbohydrate is more thermogenic than fat and energy expenditure is lower during positive energy balance produced by a diet with a high fat=carbohydrate ratio than during positive energy balance produced by a diet with a low fat=carbohydrate ratio.Randomized intervention studies comparing low fat diets to normal fat diets show that low fat diets prevent weight gain in normal weight subjects and produce weight loss in overweight individuals. In our meta-analysis of ad libitum low fat interventions we included 16 trials involving 1728 individuals. The difference in weight loss between intervention and control groups was 2.5 kg (95% CI, 1.5 -3.5; P < 0.0001). Weight loss was positively related to pre-treatment body weight (r ¼ 0.52, P < 0.05) and to reduction in percentage energy as fat (0.37 kg=%, P < 0.005). Extrapolated to a body mass index (BMI) 30 kg=m 2 , and assuming a 10% reduction in dietary fat, the predicted weight loss would be 4.4 kg (95% CI, 2.0 -6.8 kg), which has been confirmed in subsequent studies. Newer studies have shown that replacing some carbohydrate with protein may enhance weight loss. CONCLUSION: The American Paradox, the observation that obesity prevalence is increasing despite a slight decrease in population dietary fat consumption, is easily explained by the concomitantly decreasing physical activity, which reduces fat requirements and counteracts the beneficial effect of a slight reduction in dietary fat.Low fat diets with a high content of complex carbohydrates and protein do not produce any adverse effect on cardiovascular risk factors when weight loss is allowed to occur, and they have been shown to decrease mortality among high risk subjects.

Obesity in children and adolescents in Cyprus. Prevalence and predisposing factors

“…A possible explanation for the lack of relationship of food consumption and sedentary activities to obesity in this study might be the study type since cross-sectional studies are weak in such associations. 36 Even recently, a cross-sectional study indicated that energy intake was higher in non-overweight than in overweight children. 37 An interesting finding of the study is the increased risk of offspring obesity in diabetic parents.…”

Western diet increases wheel running in mice selectively bred for high voluntary wheel running

“…58 Weight gain can occur in spite of decreased food consumption when on a high-fat diet, perhaps due to differences in the efficiency of storage or thermic effects of digestion. 19,32,58,59 The WD used in this study has very high levels of saturated fats and added sucrose, both of which are considered unhealthy if ingested frequently because they can contribute to the metabolic syndrome and other chronic diseases. The impact this diet would have on health-related traits in these mice has not yet been explored, but the elevated running in HR mice may serve to ameliorate other negative effects of such a diet, much like wheel running reduced body fat in this study.…”

Les régimes hypolipidiques sont-ils utiles ?

“…Astrup [3,4] a fait deux méta-analyses des études d'intervention randomisées, durant plus de deux mois, et comparant une alimentation appauvrie en lipide et une alimentation normale en lipides, excluant toutes celles ou la perte de poids était l'objectif et utilisant un autre moyen de l'obtenir. Qu'il s'agisse des populations d'IMC de 21 à 30, ou de celles d'IMC > 25, la réduction d'environ 10 % de l'apport énergétique sous forme de lipide se traduit par une perte assez reproductible de 2,4 à 3 kg en 6 mois.…”

“…D'autres études sont venues confirmer ce phénomène qui est valable en qualité (il y a perte de poids) et en intensité (entre 2,5 et 3 kg en 6 mois). Il concerne des patients en surpoids ou obèses, les intolérants au glucose, les hommes et les femmes [3][4][5]. Cela vaut aussi pour des patients hypercholestérolémiques avec la diète « step 1 » de la NCEP où les lipides saturés sont réduits de 10 %.…”