Effect of phenylpropanolamine on energy expenditure and weight loss in overweight women.

The effect of phenylpropanolamine (PPA), a noncatecholamine sympathomimetic weight-loss agent, on energy expenditure (EE) and substrate oxidation was measured in a respiratory chamber in 24 overweight women after 4 d of treatment (PPA or placebo) during weight maintenance and after 7 wk of treatment on a hypoenergetic diet (70% of measured baseline 24-h EE). Twelve women (37 +/- 2 y, 74 +/- 6 kg, 33 +/- 1% body fat) were randomly assigned to the PPA group [75 mg osmotic release oral system (OROS)-PPA/d] and 12 (mean +/- SEM: 38 +/- 2 y, 79 +/- 1 kg, 37 +/- 1% body fat) to the placebo group. Baseline measurements of 24-h EE (7849 +/- 226 vs 7834 +/- 142 kJ/d), basal metabolic rate (BMR) and 24-h respiratory quotient (RQ) were comparable between PPA and placebo groups. After 4 d of treatment, there was no significant effect of PPA on 24-h EE, BMR, and 24-h RQ compared with placebo. Over the 7-wk diet period, however, the PPA group (n = 8) had greater weight loss than the placebo group (n = 10): -5.0 +/- 0.5 vs -3.0 +/- 0.4 kg (P < 0.05). The changes in 24-h EE and 24-h RQ over the 7 wk were not different between the groups. We conclude that weight loss is enhanced by OROS-PPA, but this change was not explained by changes in 24-h EE or 24-h RQ. The small number of subjects may have hindered detection of subtle differences in energy metabolism.

The traditional Pima Indian diet. Composition and adaptation for use in a dietary intervention study.

OBJECTIVE: To examine changes in the Pima Indian diet composition that may have played a role in the dramatic rise in the incidence of NIDDM among Pima Indians over the last century. RESEARCH DESIGN AND METHODS: We investigated the composition of the foods comparable to those available to the Pima approximately 100 yr ago, with the aim of reproducing this traditional diet as faithfully as possible for a dietary intervention study. An approximation of the traditional diet was ascertained from the ethnohistoric literature and traditional recipes. RESULTS: We estimated that the traditional Pima diet, although seasonably variable, was approximately 70-80% carbohydrate, 8-12% fat, and 12-18% protein. A diet analogous to the traditional Pima diet is largely reproducible with the foods available today. Many native foods are available locally and many commercial products can be substituted when native foods are unavailable. CONCLUSIONS: The Pima Indian diet of the last century was much higher in carbohydrate and lower in fat compared with the modern-day Pima diet. Any changes that this diabetes-prone population can make toward their traditional diet may help to decrease their incidence of diabetes.

Deterioration in carbohydrate metabolism and lipoprotein changes induced by modern, high fat diet in Pima Indians and Caucasians.

The transition from a high carbohydrate to a high fat diet may explain in part the dramatic increase in the prevalence of noninsulin-dependent diabetes mellitus among Pima Indians over the last century. In this study, 12 Pimas and 12 caucasians, all nondiabetic, were admitted to a metabolic ward and, in random order, fed 2 14-day weight-maintaining diets: a traditional Pima diet (percentage of calories: carbohydrate, 70% fat, 15%; protein, 15%) and a high fat modern diet (carbohydrate, 30%; fat, 50%; protein, 20%). Carbohydrate metabolism was characterized using the modified iv glucose tolerance test (minimal model), the acute insulin responses to arginine during a 3-step glycemic clamp, and the oral glucose tolerance test. Compared with the traditional diet, the modern diet was associated with a decrease in oral glucose tolerance (P less than 0.01) and higher plasma cholesterol concentrations (P less than 0.02). The decline in glucose tolerance was associated with similar insulin-mediated, but 23% lower glucose-mediated (P less than 0.001), glucose disposal, a 17% lower acute insulin response to glucose (P less than 0.03), a 9% lower beta-cell sensitivity to glucose (P less than 0.02), and similar beta-cell capacities. Pimas and caucasians responded similarly, except for larger changes in plasma lipids among the Pimas. Since glucose-mediated glucose disposal, beta-cell function, and glucose tolerance deteriorated on the modern diet, it is likely that diet composition affects the prevalence of noninsulin-dependent diabetes mellitus in both Pimas and caucasians.

Energy cost of physical activity on a metabolic ward in relationship to obesity.

The energy cost of physical activity on a metabolic ward was derived from the difference between the energy requirement to maintain body weight on a metabolic ward and sedentary 24-h energy expenditure measured in a respiratory chamber in 56 nondiabetic male subjects. The cost of physical activity was negatively correlated with body weight (r = -0.67, P less than 0.0001) and with percent body fat (r = -0.48, P less than 0.0005). In a subgroup of 15 subjects selected for strict weight stability (rate of daily weight change less than +/- 35 g/d), similar negative correlations were observed between energy cost of activity and body weight (r = -0.61, P less than 0.01) and percent body fat (r = -0.51, P = 0.05). The ratio of active to sedentary energy expenditure, an index of physical activity, was also negatively correlated with body weight and percent body fat (r = -0.74, P less than 0.002 and r = -0.61, P less than 0.02, respectively). These results suggest that heavier subjects on a metabolic ward are less active and expend less energy in physical activity than do lighter subjects.

Insulin-sensitive tyrosine kinase activity changes in parallel with plasma insulin and glucose concentrations in humans.

Insulin receptor tyrosine kinase is an important step in insulin action. We examined the relationship between diet-induced changes in glucose metabolism and changes in skeletal muscle insulin-sensitive tyrosine kinase activity in 12 nondiabetic subjects. Subjects were fed a traditional, high carbohydrate Pima Indian diet and a modern, high fat western diet for 2 weeks in a randomized cross-over design. At the end of each dietary period, glucose tolerance was assessed, insulin sensitivity (SI) was estimated by Bergman's minimal model method, and insulin receptor concentration and tyrosine kinase activity were determined on lectin-purified extracts from quadriceps femoris muscle. Compared to the traditional diet, the modern diet was associated with a deterioration of glucose tolerance and an increase in glucose-induced plasma insulin levels. As expected, SI changes were associated with opposite changes in plasma insulin levels. However, the changes in maximal tyrosine kinase activity were negatively correlated with changes in SI (r = -0.69; P less than 0.01) and positively correlated with changes in plasma glucose (r = 0.70; P less than 0.01) and insulin response to glucose (r = 0.57; P less than 0.025). These results suggest that the site of diet-induced changes in insulin action is beyond the insulin-sensitive tyrosine kinase. The results further suggest that the kinase activity is modulated by prevailing plasma insulin levels.

Effects of replacing saturated fat with complex carbohydrate in diets of subjects with NIDDM.

This study examined the safety of an isocaloric high-complex carbohydrate low-saturated fat diet (HICARB) in obese patients with non-insulin-dependent diabetes mellitus (NIDDM). Although hypocaloric diets should be recommended to these patients, many find compliance with this diet difficult; therefore, the safety of an isocaloric increase in dietary carbohydrate needs assessment. Lipoprotein cholesterol and triglyceride (TG, mg/dl) concentrations in isocaloric high-fat and HICARB diets were compared in 7 NIDDM subjects (fat 32 +/- 3%, fasting glucose 190 +/- 38 mg/dl) and 6 nondiabetic subjects (fat 33 +/- 5%). They ate a high-fat diet (43% carbohydrate; 42% fat, polyunsaturated to saturated 0.3; fiber 9 g/1000 kcal; cholesterol 550 mg/day) for 7-10 days. Control subjects (3 NIDDM, 3 nondiabetic) continued this diet for 5 wk. The 13 subjects changed to a HICARB diet (65% carbohydrate; 21% fat, polyunsaturated to saturated 1.2; fiber 18 g/1000 kcal; cholesterol 550 mg/day) for 5 wk. NIDDM subjects on the HICARB diet had decreased low-density lipoprotein cholesterol (LDL-chol) concentrations (107 vs. 82, P less than .001), but their high-density lipoprotein cholesterol (HDL-chol) concentrations, glucose, and body weight were unchanged. Changes in total plasma TG concentrations in NIDDM subjects were heterogeneous. Concentrations were either unchanged or had decreased in 5 and increased in 2 NIDDM subjects. Nondiabetic subjects on the HICARB diet had decreased LDL-chol (111 vs. 81, P less than .01) and unchanged HDL-chol and plasma TG concentrations).(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term energy balance: relationship with protein, carbohydrate, and fat balances.

Energy balance (energy intake-energy expenditure) is known to vary considerably on a day-to-day basis in free-living individuals. The extent to which stores of protein, carbohydrate, and fat are used to store short-term surpluses of energy and the extent to which these stores are used to make up temporary energy deficits are incompletely known. We have measured body energy balance as well as carbohydrate, fat, and protein balances in 27 Caucasian men and 27 Caucasian women over a 24-h period in a respiratory chamber. An estimated weight-maintenance diet was fed to each subject. Because of individual differences in family background, body composition, activity, and the failure of some subjects to eat all of their food, these estimates are not exact, and energy balance is rarely achieved. Energy balance was correlated with fat balance in men (r = 0.79, P less than 0.0001) and women (r = 0.72, P less than 0.0001), and the slope of this relationship was not distinguishable from unity in men (1.16 +/- 0.18) or women (0.80 +/- 0.15). There were no correlations between energy balance and either carbohydrate or protein balances. This study demonstrates that carbohydrate and protein stores are closely regulated by adjusting oxidation to intake. Thus fat, rather than carbohydrate or protein, is almost exclusively used or stored in response to day-to-day fluctuations in energy balance.