Effect of diet composition on energy expenditure during weight loss: the POUNDS LOST Study.

BACKGROUND: Weight loss reduces energy expenditure, but the contribution of different macronutrients to this change is unclear. HYPOTHESIS: We tested the hypothesis that macronutrient composition of the diet might affect the partitioning of energy expenditure during weight loss. DESIGN: A substudy of 99 participants from the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial had total energy expenditure (TEE) measured by doubly labeled water, and resting energy expenditure (REE) measured by indirect calorimetry at baseline and repeated at 6 months in 89 participants. Participants were randomly assigned to one of four diets with either 15 or 25% protein and 20 or 40% fat. RESULTS: TEE and REE were positively correlated with each other and with fat-free mass and body fat, at baseline and 6 months. The average weight loss of 8.1 ± 0.65 kg (least-square mean ± s.e.) reduced TEE by 120 ± 56 kcal per day and REE by 136 ± 18 kcal per day. A greater weight loss at 6 months was associated with a greater decrease in TEE and REE. Participants eating the high-fat diet (HF) lost significantly more fat-free mass (1.52 ± 0.55 kg) than the low-fat (LF) diet group (P<0.05). Participants eating the LF diet had significantly higher measures of physical activity than the HF group. CONCLUSION: A greater weight loss was associated with a larger decrease in both TEE and REE. The LF diet was associated with significant changes in fat-free body mass and energy expenditure from physical activity compared with the HF diet.

Reduced resting metabolic rate in patients with bulimia nervosa.

To determine whether there was a metabolic basis for recent reports that bulimic patients had low energy requirements for weight maintenance, energy expenditure measurements were made in 15 women with bulimia nervosa during abstinence from bingeing and vomiting. Resting metabolic rate, adjusted for differences in lean body mass, was significantly lower in bulimics (mean +/- SE, 4201 +/- 126 kJ/d) than healthy volunteers (4694 +/- 172 kJ/d). Bulimic patients had a blunted increase in oxygen consumption in response to low and moderate levels of exercise (421 +/- 16 and 689 +/- 17 mL/min) compared with values for healthy volunteers (491 +/- 28 and 795 +/- 26 mL/min). Plasma triiodothyronine (1.1 +/- 0.07 vs 1.4 +/- 0.08 nmol/L) levels, plasma norepinephrine levels in supine (0.58 +/- 0.04 vs 1.06 +/-0.17 nmol/L) and standing (1.34 +/- 0.15 vs 2.46 +/- 0.30 nmol/L) subjects, and the increase in norepinephrine levels during orthostatic challenge (0.76 +/- 0.15 vs 1.40 +/- 0.25 nmol/L) all were significantly less in bulimics than volunteers. These results are consistent with previous reports of decreased energy requirements for weight maintenance and decreased plasma levels of metabolism-related hormones in patients with bulimia. However, the effects of reduced energy intake in metabolic studies of patients with bulimia need to be further investigated.

Weight loss intervention in phase 1 of the Trials of Hypertension Prevention. The TOHP Collaborative Research Group.

BACKGROUND: Phase 1 of the Trials of Hypertension Prevention was a collaborative, randomized controlled clinical trial designed to determine the feasibility and efficacy of selected nonpharmacologic interventions in reducing or preventing an increase in diastolic blood pressure. METHODS: Participants aged 30 to 54 years who had a high-normal diastolic blood pressure (80 to 89 mm Hg), and were between 115% and 165% of their desirable body weight, were randomly assigned to either an 18-month weight loss intervention (n = 308) or a usual-care control condition (N = 256). Intervention consisted of 14 weekly group meetings followed by monthly maintenance sessions. Intervention participants received training in behavioral self-management technique and were asked to make life-style changes aimed at achieving a moderate reduction in energy intake and an increase in physical activity. RESULTS: The average weight losses in the intervention group at 6, 12, and 18 months of follow-up were 6.5, 5.6, and 4.7 kg for men and 3.7, 2.7, and 1.6 kg for women. The mean (+/- SE) change in diastolic blood pressure for intervention participants compared with controls at termination was -2.8 +/- 0.6 mm Hg for men and -1.1 +/- 0.9 mm Hg for women. For systolic blood pressure, the corresponding change was -3.1 +/- 0.7 mm Hg for men and -2.0 +/- 1.3 mm Hg for women. Blood pressure reductions were greater for those who lost larger amounts of weight. Sex-related differences in blood pressure response were largely due to the smaller amount of weight lost by women, and sex differences in weight loss could be accounted for by differences in baseline body weight. CONCLUSIONS: During an 18-month follow-up period, this weight reduction program was shown to be an effective nonpharmacologic intervention for reducing blood pressure in overweight adults with high-normal blood pressure.

Longitudinal correlates of change in blood pressure in adolescent girls.

The objective of this study was to assess the longitudinal changes in blood pressure in black and white adolescent girls and evaluate potential determinants of changes in blood pressure, including sexual maturation and body size. A total of 1213 black and 1166 white girls, ages 9 or 10 years at study entry, were followed up through age 14 with annual measurements of height, weight, skinfold thickness, stage of sexual maturation, systolic and diastolic blood pressures, and other cardiovascular risk factors. Average blood pressures in black girls were generally 1 to 2 mm Hg higher than in white girls of similar age over the course of the study. Age, race, stage of sexual maturation, height, and body mass index (kg/m2) were all significant univariate predictors of systolic and diastolic blood pressures in longitudinal regression analyses. Black girls had a significantly smaller increase in blood pressure for a given increase in body mass index compared with white girls. The predicted increases in blood pressure per unit increase in body mass index (mm Hg per kg/m2) were as follows: systolic, 0.65+/-0.04 in whites and 0.52+/-0.04 in blacks (P<.001); diastolic fourth Korotkoff phase, 0.31+/-0.04 in whites and 0.15+/-0.03 in blacks (P<.001); and diastolic fifth Korotkoff phase, 0.31+/-0.05 in whites and 0.16+/-0.04 in blacks (P<.001). Understanding of the determinants of the racial differences in blood pressure could provide the rationale for future interventions to reduce the excess cardiovascular mortality in black compared with white women.

The effects of carbamazepine on resting metabolic rate and thyroid function in depressed patients.

Resting metabolic rate and thyroid hormone levels were studied in 11 patients with affective disorders before and during treatment with carbamazepine (CBZ). CBZ has been previously reported to reduce thyroid hormones, but the metabolic consequence of this effect has not been explored. During CBZ treatment, thyroid hormones decreased significantly (T4, 7.53 versus 5.74 micrograms/dl, p less than 0.001), whereas the resting metabolic rate (RMR) did not (31.6 versus 30.7 kcal/m2/hr). Baseline RMRs were low and the expected positive relationship between RMR and weight was disrupted in females. The extent of previous exposure to tricyclic and monoamine oxidase inhibitors antidepressant treatment was significantly associated with lower baseline RMRs. We conclude that CBZ has no significant effect on RMR despite robust decreases in thyroid function.

Effects of bright light on resting metabolic rate in patients with seasonal affective disorder and control subjects.

Many of the symptoms of seasonal affective disorder (SAD) could be construed as having an energy-conserving function. We predicted that SAD patients would have abnormally low resting metabolic rates (RMR), which would be increased to normal levels by light therapy. To test this hypothesis we measured RMR in 10 patients on and off light treatment and 9 normal controls. Contrary to our prediction we found that SAD patients had significantly higher RMR values compared with the normal population (p less than 0.02) and these values were significantly lowered by light treatment (p less than 0.05). The possible implications of these findings are discussed.

Eating in the laboratory: is it representative?

The degree to which caloric intake of food consumed in a laboratory setting can approximate caloric intake measured under free-living conditions was assessed in the present study. Four men and four women of normal body weight weighed and recorded their food intake for four days (period 1) during which they were eating in their normal home environment. On the following week (period 2) which also lasted 4 days, the subjects consumed all their food in a laboratory setting. Based upon the findings that no significant change in body weight occurred during either period of the study, that no significant difference in paired caloric intake was observed between period 1 and period 2, and that a highly significant intraclass correlation coefficient, ri = .80 (p less than .005) existed between period 1 and period 2, it was concluded that food consumed in a laboratory setting is a reasonable approximation of caloric intake as measured under free-living conditions.

Resting metabolic rate of anorexia nervosa patients during weight gain.

To determine whether changes in energy metabolism may contribute to the difficulty of weight gain observed in anorexic patients, resting metabolic rate (RMR) and neuroendocrine function were studied in 10 patients diagnosed with anorexia nervosa. RMR per kilogram lean body mass (+/- SEM) was not significantly different from that of healthy volunteers on admission (95.9 +/- 5.6 vs 103.6 +/- 3.3 kJ/kg, respectively), during early refeeding (108.6 +/- 6.9 kJ/kg), or at target weight (102.1 +/- 3.8 kJ/kg). At late refeeding RMR was significantly higher (132.1 +/- 4.9 kJ/kg, P < 0.0001). There were no significant correlations between plasma norepinephrine and thyroid hormones and RMR. The rise in RMR during refeeding is at least double that observed in other studies in which normal-weight subjects are experimentally overfed or experimentally underfed and then refed. These results suggest that the increase in RMR during refeeding is disproportionate to weight gain and this large magnitude of increase may be unique to anorexia nervosa.

Relative importance of calorie intake needed to gain weight and level of physical activity in anorexia nervosa.

We assessed whether level of physical activity of anorexia nervosa patients could influence caloric consumption needed to gain weight during hospitalization. Seventy-three percent of patients with anorexia nervosa had higher levels of motor activity than did healthy female volunteers. Anorectics required 8301 +/- 2272 kcal (mean +/- SD) to gain 1 kg body wt. Activity levels and caloric consumption needed to gain 1 kg were significantly correlated; the most active patients needed to consume more calories to gain weight. A median split of anorectic patients by level of activity showed that the group with lower activity levels gained 1 kg every 5.1 +/- 1.2 d, whereas the group with higher activity levels gained 1 kg every 7.2 +/- 1.9 d. These data suggest that the rate of weight gain can be accelerated, and the cost of hospitalization decreased, by restricting exercise in anorectics during refeeding.

Effects of aerobic exercise and weight loss on riboflavin requirements of moderately obese, marginally deficient young women.

In a previous study, exercise was shown to increase riboflavin requirements of active, normal weight young women. The present study examined the effect of exercise and weight loss on riboflavin status of moderately overweight women. The experiment was designed as a two-period cross-over with an initial base-line period and two 5-wk metabolic periods. The basic diet contained 1200 kcal with a riboflavin concentration of 0.8 mg/1000 kcal. Exercise consisted of a program of dance exercise. Riboflavin depletion, as measured by increased erythrocyte glutathione reductase activity coefficients and decreased urinary excretion of riboflavin, occurred during both nonexercise and exercise periods. Erythrocyte glutathione reductase activity coefficients increased from a base-line mean of 1.28 +/- 0.11 to 1.40 +/- 0.12 during nonexercise and to 1.49 +/- 0.16 during exercise. Urinary excretion of riboflavin fell from 48 +/- 12% of intake during base-line to 30 +/- 13% during nonexercise and to 19 +/- 6% during exercise. Riboflavin depletion was not related to the rate or composition of weight loss or to change in aerobic capacity.

Caloric intake necessary for weight maintenance in anorexia nervosa: nonbulimics require greater caloric intake than bulimics.

In the past decade, patients with anorexia nervosa have been subdivided by the presence or absence of binging-and-purging behavior. Psychologic, physiologic, and premorbid weight differences have also been discovered between these subgroups. We now report that nonbulimic anorectics required 30-50% more caloric intake than bulimic anorectics to maintain a stable weight. This difference in caloric intake was independent of phase of illness; it was present at low weight and at intervals after weight restoration. Subjects were closely supervised on an inpatient hospital ward so that they could not binge or purge. Motor activity did not appear to explain these alterations in caloric requirements. Such differences in caloric intake could be trait related or a consequence of many years of starving or binging behavior. These findings are clinically relevant for advising eating disorder patients of caloric requirements necessary to maintain a normal weight.

Effects of exercise on riboflavin requirements of young women.

The riboflavin requirement of young women during periods of sedentary living and exercise was determined during a 12-wk metabolic study. The study was divided into a 6-wk no exercise period followed by a 6-wk exercise period in which subjects jogged around a track for 20 to 50 min/day. Twelve subjects, aged 19 to 27 yr, were fed a basic diet containing 0.6 mg riboflavin/1000 kcal of intake. Riboflavin intake was increased by 0.2 mg/1000 kcal increments by provision of riboflavin in a glucose polymer mixture. Linear regression analysis was used to estimate the riboflavin intake required for an erythrocyte glutathione reductase activity coefficient of 1.25 during both the no exercise and exercise periods. Individual riboflavin requirements ranged from 0.62 to 1.21 mg/1000 kcal before exercise and 0.63 to 1.4 mg/1000 kcal during the exercise periods. Riboflavin requirement could not be related to the kilocalorie intake or lean body mass of the subjects. It is concluded that healthy young women require more riboflavin to achieve biochemical normality than the 1980 Recommended Dietary Allowances and that exercise increases riboflavin requirements.

Effects of exercise on riboflavin requirements: biological validation in weight reducing women.

The present study was designed to evaluate our previous estimates for riboflavin requirement, 0.96 mg/1000 kcal during nonexercise and 1.16 mg/1000 kcal during exercise in overweight women. Two groups of 6 weight reducing women consumed either 1.16 mg riboflavin/1000 kcal (HR) or 0.96 mg/1000 kcal (MR). The study was two, 3 period by 2 treatment (exercise or nonexercise) crossover designs, one design at each level of riboflavin. Erythrocyte glutathione reductase activity coefficients (AC) significantly increased in both groups from 1.16 +/- .02 to 1.20 +/- .03 in group HR and from 1.31 +/- .04 to 1.36 +/- .02 in the MR group during nonexercise and exercise, respectively. ACs increased in the HR group due to an increase in total enzyme activity while ACs increased in the MR group due to a decrease in basal enzyme activity reflecting decreased flavin availability. There were no differences in aerobic capacity, weight loss, nor change in lean body mass between the two groups. Thus, 0.96 mg/1000 kcal was not adequate during either nonexercise or exercise periods while the 1.16 mg/1000 kcal was adequate.

Weight-loss experience of black and white participants in NHLBI-sponsored clinical trials.

We examined race-specific weight-loss results from two randomized, multicenter trials; the Hypertension Prevention Trial (HPT) and the Trials of Hypertension Prevention (TOHP). Mean weight change from baseline averaged 2.2 kg less in black women than in white women during 18 mo of follow-up in TOHP and 2.7 kg less during 36 mo of follow-up in HPT. Mean weight loss averaged 2.0 kg less in black than in white men in TOHP and 1.4 kg less in HPT. Because of greater weight gain in black control subjects, a comparison of net weight loss (change in intervention minus change in control participants, within-race) showed a less marked difference than did black-white differences in weight loss within the actively treated group. Thus, relative to weight that would have been gained without the intervention, the experience of blacks and whites was more similar. Racial differences in weight loss may result from a combination of behavioral, sociocultural, biological, and programmatic factors.

Energy intake and physical activity in relation to indexes of body fat: the National Heart, Lung, and Blood Institute Growth and Health Study.

The relationship between energy intake, physical activity, and body fat was investigated in the baseline visit of 2379 black and white girls aged 9-10 y enrolled in the National Heart, Lung, and Blood Institute Growth and Health Study. Three-day food records, three-day physical activity diaries, physical-activity-patterns questionnaires, and an assessment of the number of hours of television and video watched were obtained. Multivariate-regression analyses showed that age, the number of hours of television and video watched, the percent of energy from saturated fatty acids, and the activity-patterns score best explained the variation in body mass index and sum of three skin-fold-thickness measurements for black girls. The best model for white girls included age, the number of hours of television and video watched, and the percent of energy from total fat. These results indicate that body fatness is related to energy intake and expenditure in both black and white girls. Longitudinal studies will help assess the value of these variables in predicting changes in body fat.

Decreased caloric intake in normal-weight patients with bulimia: comparison with female volunteers.

Patients with bulimia (binge-purge syndrome) frequently complain that they consume a very restrictive diet to avoid gaining weight. To investigate this claim, 23 hospitalized bulimic patients were assessed daily for body weight, caloric intake, macronutrient diet content, activity measures, and body composition estimates during weight-stable periods. Bulimic patients ate fewer kilocalories per kilogram body weight (22.1 +/- 4.6 kcal/kg) than did age-matched normal women (29.7 +/- 6.5 kcal/kg) but had similar activity levels and body composition. Clinical variables, such as history of laxative abuse, anorexia, or obesity, and physiological characteristics, such as body weight, activity level, or dietary content, could not account for this difference in caloric consumption. Bulimic patients tended to eat a diet lower in fat and higher in protein than did control subjects. These results agree with observations of increased efficiency of caloric utilization in obese patients and support patient complaints of a tendency to gain weight easily.

Efficacy and safety of lowering dietary intake of total fat, saturated fat, and cholesterol in children with elevated LDL cholesterol: the Dietary Intervention Study in Children.

BACKGROUND: Few studies have shown the efficacy and safety of lower-fat diets in children. OBJECTIVE: Our objective was to assess the efficacy and safety of lowering dietary intake of total fat, saturated fat, and cholesterol to decrease LDL-cholesterol concentrations in children. DESIGN: A 6-center, randomized controlled clinical trial was carried out in 663 children aged 8-10 y with LDL-cholesterol concentrations greater than the 80th and less than the 98th percentiles for age and sex. The children were randomly assigned to either an intervention group or a usual care group. Behavioral intervention promoted adherence to a diet providing 28% of energy from total fat, <8% from saturated fat,

Effects on blood lipids of a blood pressure-lowering diet: the Dietary Approaches to Stop Hypertension (DASH) Trial.

BACKGROUND: Effects of diet on blood lipids are best known in white men, and effects of type of carbohydrate on triacylglycerol concentrations are not well defined. OBJECTIVE: Our goal was to determine the effects of diet on plasma lipids, focusing on subgroups by sex, race, and baseline lipid concentrations. DESIGN: This was a randomized controlled outpatient feeding trial conducted in 4 field centers. The subjects were 436 participants of the Dietary Approaches to Stop Hypertension (DASH) Trial [mean age: 44.6 y; 60% African American; baseline total cholesterol: < or = 6.7 mmol/L (< or = 260 mg/dL)]. The intervention consisted of 8 wk of a control diet, a diet increased in fruit and vegetables, or a diet increased in fruit, vegetables, and low-fat dairy products and reduced in saturated fat, total fat, and cholesterol (DASH diet), during which time subjects remained weight stable. The main outcome measures were fasting total cholesterol, LDL cholesterol, HDL cholesterol, and triacylglycerol. RESULTS: Relative to the control diet, the DASH diet resulted in lower total (-0.35 mmol/L, or -13.7 mg/dL), LDL- (-0.28 mmol/L, or -10.7 mg/dL), and HDL- (-0.09 mmol/L, or -3.7 mg/dL) cholesterol concentrations (all P < 0.0001), without significant effects on triacylglycerol. The net reductions in total and LDL cholesterol in men were greater than those in women by 0.27 mmol/L, or 10.3 mg/dL (P = 0.052), and by 0.29 mmol/L, or 11.2 mg/dL (P < 0.02), respectively. Changes in lipids did not differ significantly by race or baseline lipid concentrations, except for HDL, which decreased more in participants with higher baseline HDL-cholesterol concentrations than in those with lower baseline HDL-cholesterol concentrations. The fruit and vegetable diet produced few significant lipid changes. CONCLUSIONS: The DASH diet is likely to reduce coronary heart disease risk. The possible opposing effect on coronary heart disease risk of HDL reduction needs further study.

Weight modification efforts reported by black and white preadolescent girls: National Heart, Lung, and Blood Institute Growth and Health Study.

OBJECTIVE: This study tested four hypotheses: (1) a high percentage of 9- and 10-year-old girls are already trying to lose weight; (2) more white tha black girls are trying to lose weight; (3) more black than white girls are trying to gain weight; and (4) weight modification efforts of preadolescent girls are influenced by factors other than race, such as maternal criticism, body dissatisfaction, and socioeconomic status. DESIGN: Cross-sectional analysis of baseline data on 2379 girls 9 and 10 years of age, which consisted of 1213 black and 1166 white enrollees. RESULTS: Black girls were taller and heavier and showed earlier signs of puberty than white girls but were less dissatisfied with their weight, body shape, and body parts. Approximately 40% of 9- and 10-year-old girls reported that they were trying to lose weight. Of those girls classified in the fourth quartile of body mass index (BMI), approximately 75% were trying to lose weight. After adjusting for BMI, no significant black and white differences in the prevalence of those trying to lose weight were seen, but significantly more black than white girls were trying to gain weight. Multiple logistic regression identified a high BMI, the mother telling her she was too fat, and body dissatisfaction as the major factors associated with trying to lose weight. However, chronic dieting was only associated with a high BMI and the mother telling her she was too fat. An important predictor of girls who were trying to gain weight was being black, along with having a low BMI and the mother telling her she was too thin. CONCLUSIONS: Attempts at gaining weight are much more frequent among black preadolescent girls than their white counterparts. No racial difference was found between black and white girls in their efforts to lose weight or to practice chronic dieting. Because approximately 40% of 9- and 10-year-old girls are already trying to lose weight, pediatricians should capitalize on this concern by providing information on proper weight control techniques. Educational efforts should be directed to both the mother and the child, because weight control efforts of preadolescent girls are stimulated by their mothers' admonitions of being too fat or too thin. The high prevalence of dieting among the thinnest adolescent girls also needs to be addressed by pediatricians.

The effects of race, household income, and parental education on nutrient intakes of 9- and 10-year-old girls. NHLBI Growth and Health Study.

Nutrient intakes of 2149 black and white, 9- and 10-year-old girls varied by race, household income, and parental education. Of the three variables, higher education was most consistently associated with more desirable levels of nutrient intakes, that is, lower percentage of dietary fat and higher levels of vitamin C, calcium, and potassium. Higher income was related to higher intakes of vitamin C, but lower intakes of calcium and iron. Higher income was associated with lower percentage of dietary fat. After adjustment for income and education, race was associated with intakes of calcium, vitamin C, and to a lesser extent, percentages of kilocalories from total fat and polyunsaturated fat, and potassium. Black girls had a significantly lower intake of calcium (720 versus 889 mg) and a higher intake of vitamin C (91 versus 83 mg). Proportions of the cohort with inadequate or excessive intakes of micronutrients and macronutrients were also estimated. A high proportion of girls exceeded the recommended intake level of 30% of kilocalories from total fat (90% of black girls; 84% of white girls) and 10% of kilocalories from saturated fat (92 and 93%, respectively). Low intakes of calcium (40% of black girls and and 20% og white girls) and zinc (36 and 38%, respectively) commonly were found for girls of both names.