Substitution of saturated with monounsaturated fat in a 4-week diet affects body weight and composition of overweight and obese men.
A randomised crossover study of eight overweight or obese men (aged 24-49 years; BMI 25.5-31.3 kg/m(2)); who followed two diets for 4 weeks each; was performed to determine whether substitution of saturated fat with monounsaturated fat affects body weight and composition. Subjects were provided with all food and beverages as modules (selected ad libitum) of constant macronutrient composition; but differing energy content. The % total energy from saturated fat; monounsaturated fat and polyunsaturated fat was 24; 13 and 3 % respectively on the saturated fatty acid (SFA)-rich diet and 11; 22 and 7 % respectively on the monounsaturated fatty acid (MUFA)-rich diet. MUFA accounted for about 80 % of the unsaturated fats consumed on both diets. Body composition; blood pressure; energy expenditure (resting and postprandial metabolic rates; substrate oxidation rate; physical activity); serum lipids; the fatty acid profile of serum cholesteryl esters and plasma glucose and insulin concentrations were measured before and after each diet period. Significant (P< or =0.05) differences in total cholesterol and the fatty acid composition of serum cholesteryl esters provided evidence of dietary adherence. The men had a lower weight (-2.1 (SE 0.4) kg; P=0.0015) and fat mass (-2.6 (SE 0.6) kg; P=0.0034) at the end of the MUFA-rich diet as compared with values at the end of the SFA-rich diet. No significant differences were detected in energy or fat intake; energy expenditure; substrate oxidation rates or self-reported physical activity. Substituting dietary saturated with unsaturated fat; predominantly MUFA; can induce a small but significant loss of body weight and fat mass without a significant change in total energy or fat intake.
Nuts; body weight and insulin resistance.
Traditionally; nuts have been considered a staple food; but because of their high energy and fat content are not considered good for body weight control or insulin sensitivity. Frequent consumption of nuts reduces the risk of coronary artery disease and type-2 diabetes and nut-enriched diets favourably alter blood lipids in normal and hypercholesterolemic individuals under controlled and free-living dietary conditions. However; whether or not frequent consumption of nuts can cause weight gain and impair insulin sensitivity is not fully understood. Review of the available data to date suggests that adding nuts to habitual diets of free-living individuals does not cause weight gain. In fact; nuts have a tendency to lower body weight and fat mass. In the context of calorie-restricted diets; adding nuts produces a more lasting and greater magnitude of weight loss among obese subjects while improving insulin sensitivity. Further studies are needed to clarify the effect of long-term (>/= year) consumption of nuts on body weight and their role in altering insulin sensitivity both in normal and type-2 diabetics. In the meantime; there is sufficient evidence to promote the inclusion of nuts as part of healthy diets.
Effects of moderate-fat (from monounsaturated fat) and low-fat weight-loss diets on serum lipid profile in overweight and obese men and women.
BACKGROUND: Little evidence of the effects of moderate-fat (from monounsaturated fat) weight-loss diets on risk factors for cardiovascular disease exists because low-fat diets are typically recommended. Previous studies in weight-stable persons showed that a moderate-fat diet results in a more favorable lipid and lipoprotein profile (ie; lower serum triacylglycerol and higher HDL cholesterol) than does a low-fat diet. OBJECTIVE: We evaluated the effects of energy-controlled; low-fat and moderate-fat diets on changes in lipids and lipoproteins during weight loss and subsequent weight maintenance. DESIGN: We conducted a parallel-arm study design in overweight and obese [body mass index (in kg/m(2)): 29.8 +/- 2.4] healthy men and women (n = 53) assigned to consume a low-fat (18% of energy) or moderate-fat (33% of energy) diet for 6 wk to achieve weight loss; which was followed by 4 wk of weight maintenance. All foods were provided and body weight was monitored to ensure equal weight loss between groups. RESULTS: The moderate-fat diet elicited favorable changes in the lipoprotein profile. Compared with baseline; HDL cholesterol was unchanged; whereas triacylglycerol and the ratios of total and non-HDL cholesterol to HDL cholesterol were lower at the end of the weight-maintenance period in the moderate-fat diet group. Despite similar weight loss; triacylglycerol rebounded; HDL cholesterol decreased; and the ratios of total and non-HDL cholesterol to HDL cholesterol did not change during the 10-wk interval in the low-fat diet group. CONCLUSIONS: A moderate-fat weight-loss and weight-maintenance diet improves the cardiovascular disease risk profile on the basis of favorable changes in lipids and lipoproteins. There is merit in recommending a moderate-fat weight-loss diet.
A randomized controlled trial of a moderate fat; low energy diet compared with a low fat; low energy diet for weight loss in overweight adults.
CONTEXT: Long-term success in weight loss with dietary treatment has been elusive. OBJECTIVE: To evaluate a diet moderate in fat based on the Mediterranean diet compared to a standard low-fat diet for weight loss when both were controlled for energy. DESIGN: A randomized; prospective 18 month trial in a free-living population. PATIENTS: A total of 101 overweight men and women (26.5-46 kg/m(2)). INTERVENTION: (1) Moderate-fat diet (35% of energy); (2) low-fat diet (20% of energy). MAIN OUTCOME MEASUREMENTS: Change in body weight. RESULTS: After 18 months; 31/50 subjects in the moderate-fat group; and 30/51 in the low fat group were available for measurements. In the moderate-fat group; there were mean decreases in body weight of 4.1 kg; body mass index of 1.6 kg/m(2); and waist circumference of 6.9 cm; compared to increases in the low-fat group of 2.9 kg; 1.4 kg/m(2) and 2.6 cm; respectively; P < or = 0.001 between the groups. The difference in weight change between the groups was 7.0 kg. (95% CI 5.3; 8.7). Only 20% (10/51) of those in the low-fat group were actively participating in the weight loss program after 18 months compared to 54% (27/50) in the moderate-fat group; (P<0.002). The moderate-fat diet group was continued for an additional year. The mean weight loss after 30 months compared to baseline was 3.5 kg (n = 19; P = 0.03). CONCLUSIONS: A moderate-fat; Mediterranean-style diet; controlled in energy; offers an alternative to a low-fat diet with superior long-term participation and adherence; with consequent improvements in weight loss.
Effects of food attributes on hunger and food intake.
OBJECTIVE: To explore the relative importance of a food's macronutrient composition; energy value; energy density; fiber content; weight; volume; sensory properties and rheology on hunger and food intake. DESIGN: Preloads of peanuts; peanut butter (rheology control); almonds (tree nut); chestnuts (macronutrient control); chocolate (sensory control); rice cakes (volume control); pickles (weight control) and no load (time control) were consumed by subjects in random order at weekly intervals and hunger was assessed over the subsequent 180 min. Free-feeding energy and macronutrient intake were monitored 24 h before and following preload ingestion. SUBJECTS: Twelve male and 12 female healthy; normal weight (12-28% body fat); adults (mean (s.d.) age 22 +/- 2.5 y) with low dietary restraint. RESULTS: Hunger ratings following consumption of the 2092 kJ (500 kcal) preloads of peanuts; peanut butter; almonds; chestnuts and chocolate were significantly lower than the low energy preloads or no preload condition; but with the exception of peanut butter; did not vary from each other. The rate of hunger recovery was consistent across all preloads so the overall impact of each food on hunger was determined by the initial drop it evoked. Total energy; but not macronutrient; compensation was observed with all preloads. Consequently; the fatty acid profile of the total diet reflected the composition of the preloads. CONCLUSIONS: Energy content may be the primary determinant of a food's impact on hunger. Because macronutrient compensation is weak; a dietary supplement or substitute may influence the daily dietary nutrient profile.
Effect of chronic consumption of almonds on body weight in healthy humans
Small changes of diet may reduce CVD risk. One example is the inclusion of nuts. They are rich in fiber; unsaturated fatty acids and phytonutrients. However; their fat content and energy density raise concerns that chronic consumption will promote weight gain. Randomized intervention studies are required to evaluate whether this concern is well founded. This study's aim was to determine if the inclusion of a 1440 kJ serving of almonds in the daily diet results in positive energy balance; and body composition change. During a 23-week cross-over design study; participants were required to consume almonds for 10 weeks and were provided no advice on how to include them in their diet. For another 10 weeks (order counter-balanced); participants followed their customary diet and there was a 3-week washout between. The study group consisted of twenty women. Potential mechanisms of energy dissipation were measured. Ten weeks of daily almond consumption did not cause a change in body weight. This was predominantly due to compensation for the energy contained in the almonds through reduced food intake from other sources. Moreover; inefficiency in the absorption of energy from almonds was documented (P < 0.05). No changes in resting metabolic rate; thermic effect of food or total energy expenditure were noted. A daily 1440 kJ serving of almonds; sufficient to provide beneficial effects on cardiovascular risk factors; may be included in the diet with limited risk of weight gain. Whether this can be generalized to other high-fat energy dense foods warrants evaluation.