Effect of a low-glycaemic index--low-fat--high protein diet on the atherogenic metabolic risk profile of abdominally obese men.

It has been suggested that the current dietary recommendations (low-fat-high-carbohydrate diet) may promote the intake of sugar and highly refined starches which could have adverse effects on the metabolic risk profile. We have investigated the short-term (6-d) nutritional and metabolic effects of an ad libitum low-glycaemic index-low-fat-high-protein diet (prepared according to the Montignac method) compared with the American Heart Association (AHA) phase I diet consumed ad libitum as well as with a pair-fed session consisting of the same daily energy intake as the former but with the same macronutrient composition as the AHA phase I diet. Twelve overweight men (BMI 33.0 (sd 3.5) kg/m2) without other diseases were involved in three experimental conditions with a minimal washout period of 2 weeks separating each intervention. By protocol design, the first two conditions were administered randomly whereas the pair-fed session had to be administered last. During the ad libitum version of the AHA diet, subjects consumed 11695.0 (sd 1163.0) kJ/d and this diet induced a 28 % increase in plasma triacylglycerol levels (1.77 (sd 0.79) v. 2.27 (sd 0.92) mmol/l, P<0.05) and a 10 % reduction in plasma HDL-cholesterol concentrations (0.92 (sd 0.16) v. 0.83 (sd 0.09) mmol/l, P<0.01) which contributed to a significant increase in cholesterol:HDL-cholesterol ratio (P<0.05), this lipid index being commonly used to assess the risk of coronary heart disease. In contrast, the low-glycaemic index-low-fat-high-protein diet consumed ad libitum resulted in a spontaneous 25 % decrease (P<0.001) in total energy intake which averaged 8815.0 (sd 738.0) kJ/d. As opposed to the AHA diet, the low-glycaemic index-low-fat-high-protein diet produced a substantial decrease (-35 %) in plasma triacylglycerol levels (2.00 (sd 0.83) v. 1.31 (sd 0.38) mmol/l, P<0.0005), a significant increase (+1.6 %) in LDL peak particle diameter (251 (sd 5) v. 255 (sd 5) A, P<0.02) and marked decreases in plasma insulin levels measured either in the fasting state, over daytime and following a 75 g oral glucose load. During the pair-fed session, in which subjects were exposed to a diet with the same macronutrient composition as the AHA diet but restricted to the same energy intake as during the low-glycaemic index-low-fat-high-protein diet, there was a trend for a decrease in plasma HDL-cholesterol levels which contributed to the significant increase in cholesterol:HDL-cholesterol ratio noted with this condition. Furthermore, a marked increase in hunger (P<0.0002) and a significant decrease in satiety (P<0.007) were also noted with this energy-restricted diet. Finally, favourable changes in the metabolic risk profile noted with the ad libitum consumption of the low-glycaemic index-low-fat-high-protein diet (decreases in triacyglycerols, lack of increase in cholesterol:HDL-cholesterol ratio, increase in LDL particle size) were significantly different from the response of these variables to the AHA phase I diet. Thus, a low-glycaemic index-low-fat-high-protein content diet may have unique beneficial effects compared with the conventional AHA diet for the treatment of the atherogenic metabolic risk profile of abdominally obese patients. However, the present study was a short-term intervention and additional trials are clearly needed to document the long-term efficacy of this dietary approach with regard to compliance and effects on the metabolic risk profile.     

Evidence for impaired lipolysis in abdominally obese men: postprandial study of apolipoprotein B-48- and B-100-containing lipoproteins

BACKGROUND: Abdominal obesity has been associated with postprandial hypertriglyceridemia. The contribution of intestinally and hepatically derived lipoproteins to this exaggerated postprandial lipemic response is not known. OBJECTIVE: We examined the associations between body fatness, fat distribution, and postprandial apolipoprotein (apo) B-48 and apo B-100 concentrations measured in triacylglycerol-rich lipoproteins (TRLs). DESIGN: Dietary fat tolerance was investigated in 50 men aged 28-67 y. The subjects were given a test meal containing 60 g fat/m(2) body surface area and providing 64% of energy from fat, 18% from carbohydrates, and 18% from protein. The meal provided 7524-9196 kJ, depending on body surface area. Blood samples were collected every 2 h over an 8-h period. RESULTS: The increase in plasma triacylglycerol after the meal resulted from increases in both apo B-48- and apo B-100-containing lipoproteins. The apo B-100 concentration was the strongest contributor (R(2) = 69.6%, P = 0.0001) to postprandial triacylglycerol in total TRLs; the postprandial increase in triacylglycerol was best predicted by the apo B-48 concentration (R(2) = 32.7%, P = 0.0001). Visceral abdominal fat was significantly associated with high postprandial TRL apo B-48 and apo B-100 concentrations (r = 0.30-0.44, P < 0.05). After the meal, the apo B-100 concentration in small TRLs decreased in 12 subjects. These men showed features of the insulin resistance-dyslipidemic syndrome, including more visceral fat (P = 0.07) and an altered fasting metabolic profile. CONCLUSION: A lower lipolytic capacity may contribute to the exaggerated and prolonged postprandial lipemia among abdominally obese men.     

Blunted lipolytic response to fasting in abdominally obese women: evidence for involvement of hyposomatotropism

BACKGROUND: Abdominal obesity is associated with a blunted lipolytic response to fasting that may contribute to the preservation of adipose tissue mass. OBJECTIVE: To further explore the pathophysiology of blunted lipolysis during fasting in obesity, we simultaneously measured lipolysis and distinct neuroendocrine regulatory hormones in abdominally obese and normal-weight (NW) women. DESIGN: Eight abdominally obese [x +/- SD body mass index (BMI; in kg/m(2)): 32.1 +/- 2.6] and 6 NW (BMI: 22.7 +/- 1.5) women were studied during the last 8 h of a 20-h fast. The glycerol appearance rate and the serum and plasma concentrations of insulin, leptin, cortisol, and growth hormone were measured regularly. RESULTS: At 13 h of fasting, the mean (+/-SD) glycerol appearance rate corrected for fat mass was greater in NW women than in obese women (7.2 +/- 1.0 and 5.1 +/- 0.6 micro mol.kg(-1).min(-1), respectively; P = 0.001). After a 20-h fast, lipolysis increased to 8.9 +/- 1.5 mmol.kg(-1).min(-1) in NW women (23%), whereas it did not change significantly in obese women (-2%). Fasting decreased insulin concentrations by approximately 30% in both groups, but it did not induce significant changes in leptin concentrations. Mean cortisol concentrations and urinary catecholamine excretion were comparable in both groups. However, mean plasma growth hormone concentrations were higher in NW women than in obese women (1.81 +/- 0.98 compared with 0.74 +/- 0.52 mU/L; P = 0.046). The relative change in lipolysis tended to correlate with mean plasma growth hormone concentrations (r = 0.515, P = 0.059). CONCLUSION: Abdominal obesity-associated hyposomatotropism may be involved in the blunted increase in lipolysis during fasting.     

Glycemic index predicts individual glucose responses after self-selected breakfasts in free-living, abdominally obese adults

The degree to which an individual's glycemic response to a meal is determined by the glycemic index (GI) and other components of the meal remains unclear, especially when meals are not consumed in a highly controlled research setting. To address this question, we analyzed data collected during the run-in period of a clinical trial. Free-living, nondiabetic adults (n = 57) aged 53.9 ± 9.8 y (mean ± SD) with a BMI of 33.9 ± 5.3 kg/m(2) and waist circumference of 109 ± 11 cm underwent a 75-g oral glucose tolerance test (OGTT) and, on a separate day, wore a continuous glucose-monitoring system (CGMS) for 24 h during which time they recorded all foods consumed. The protein, fat, and available carbohydrate (avCHO) content and GI of the breakfast meals were calculated from the food records and the incremental areas under the glycemic response curves (iAUC) for 2 h after breakfast (iAUC(breakfast)) were calculated from CGMS data. Values for iAUC(breakfast), avCHO, fat, fiber, and BMI were normalized by log-transformation. The ability of participant characteristics and breakfast composition to predict individual iAUC(breakfast) responses was determined using step-wise multiple linear regression. A total of 56% of the variation in iAUC(breakfast) was explained by GI (30%; P < 0.001), iAUC after the OGTT (11%; P < 0.001), avCHO (11%; P < 0.001), and waist circumference (3%; P = 0.049); the effects of fat, protein, dietary fiber, age, sex, and BMI were not significant. We concluded that, in free-living, abdominally obese adults, GI is a significant determinant of individual glycemic responses elicited by self-selected breakfast meals. In this study, GI was a more important determinant of glycemic response than carbohydrate intake.     

Androgen levels and sex functions in testosterone-treated hypogonadal men

This study investigated the correlation of sex functions in testosterone-treated hypogonadal men and in tamoxifen-treated eugonadal men in relation to blood androgen levels. Self-reported sex functions in men treated with parenteral testosterone esters (levels fall very rapidly with this type of substitution therapy) declined at levels ranging between 11 and 5 nmole/L of testosterone. Although wide variations in individual responses were noted, levels of response in given individuals appeared to be reproducible. The critical level for oral testosterone undecanoate lies between 4 and 6 nmole/L testosterone, although the relatively high levels of dihydrotestosterone in testosterone undecanoate therapy probably produce an additive effect upon sex functions. Dihydrotestosterone is capable of maintaining sex functions in hypogonadal men. There is no evidence in this study design that androgen administration in excess of the individually determined critical levels further enhances sex functions. In view of the rapidly declining blood levels of androgens with the available parenteral testosterone ester preparations, the results suggest that hypogonadal patients may benefit from a more frequent administration of these preparations.     

Short-term orlistat treatment does not affect mineral balance and bone turnover in obese men

Orlistat is a gastrointestinal lipase inhibitor that is used to reduce dietary fat absorption and to enhance weight loss in subjects consuming a hypocaloric diet. To assess whether orlistat has an effect on the metabolism of six minerals, a 21-d, double-blind, randomized, parallel-group, placebo-controlled mineral balance study was conducted in obese (body mass index > 30 kg/m(2)) men. Subjects consumed a hypocaloric diet with a constant daily mineral content and received daily oral treatment with orlistat (120 mg three times daily) (n = 14) or placebo (three times daily) (n = 14) for 21 d. After a 14-d equilibration period, calcium, phosphorus, magnesium, iron, copper and zinc balances were assessed for d 15-21. In addition, the effect of diet and orlistat treatment on bone metabolism was estimated from measurement of biomarkers of bone formation and bone resorption. Serum and urine electrolytes were also measured at baseline and at the end of treatment. Orlistat inhibited fat absorption by approximately 33% (P < 0.05). There were no significant differences in mineral apparent absorption, urinary mineral loss or mineral balance between the orlistat and placebo groups. Markers of bone turnover and serum and urine electrolytes did not differ between the orlistat and placebo groups. Orlistat was well tolerated; adverse events were of mild or moderate intensity, and the majority of these events were unrelated or remotely related to study treatment. In obese men consuming a hypocaloric diet, the administration of orlistat had no significant effect on the balance of six selected minerals. In addition, biomarkers of bone turnover, as well as serum and urine electrolytes, were not affected by orlistat treatment.     

Reduced fertility among overweight and obese men

BACKGROUND: Overweight and obese men have been reported to have lower sperm counts and hormonal changes, but data are lacking regarding effects on couple fertility. METHODS: We examined the relationship between male body mass index (BMI) and infertility in couples enrolled in the Agricultural Health Study in the United States. The analysis sample was limited to couples (wife <40 years old) with an attempt at pregnancy in the last 4 years based on pregnancy and fertility data provided by wives. Infertility was defined as not conceiving a pregnancy after at least 12 months of unprotected intercourse regardless of whether or not a pregnancy ultimately occurred. Self-reported weight and height were used to calculate BMI (kg/m). Adjusted odds ratios (aORs) for infertility associated with increases in male BMI were calculated with logistic regression. RESULTS: Adjusting for potential confounders, a 3-unit increase in male BMI was associated with infertility (aOR = 1.12; 95% confidence interval = 1.01-1.25; n = 1329). There was a dose-response relationship, and the BMI effect was stronger when the data were limited to couples with the highest-quality infertility data. The association between BMI and infertility was similar for older and younger men, suggesting that erectile dysfunction in older men does not explain the association. CONCLUSIONS: This report of lower fertility in overweight and obese men needs replication. If the findings are robust, programs to prevent obesity may improve men's reproductive health and save medical costs for infertility treatment.     

Weight loss of obese men compared with women

Men are believed to lose more weight than women. Factors supporting this belief include men's greater weight at the start of treatment and measurement of weight loss in terms of kilograms lost rather than percent of overweight lost. No sex differences in weight loss 1 year after surgery for obesity were observed when men and women were matched preoperatively by weight or overweight. When the total sample was considered, men weighed significantly more than women preoperatively and lost significantly more kilograms postoperatively.     

Influence of methylphenidate on eating in obese men

OBJECTIVE: Rapid synaptic dopamine transport or reduced brain dopamine receptor signaling may influence energy intake. Methylphenidate, a dopamine reuptake inhibitor, increases brain synaptic dopamine and produces anorexia, suggesting that it may reduce energy intake. We investigated the effects of two doses of short-acting methylphenidate on energy intake over one meal in obese adult males. RESEARCH METHODS AND PROCEDURES: Nine obese males (>85th BMI percentile) ingested a placebo or a moderate dose (0.5 mg/kg) or a high dose (1.0 mg/kg) of methylphenidate in a within-subject double-blind acute laboratory study. One hour after ingestion, pizza consumption was measured in a naturalistic laboratory setting. RESULTS: Participants reduced energy intake by 23% for the moderate dose vs. the placebo (p < 0.02), but there was no significant difference for the high dose vs. the moderate dose (p > 0.05). Participants consumed 34% fewer kilocalories after ingesting the lowest effective dose of methylphenidate compared with placebo (725.7 +/- 404.5 vs.1095 +/- 271.1 kcal, p < 0.01). Seven of nine subjects responded to the moderate dose. The increase in perceived drug effect above placebo was correlated with the reduction in energy intake for both the moderate (r = -0.85, p = 0.004) and the high (r = -0.75 p = 0.021) doses. Hunger scores were not different across drug doses or placebo before drug administration. DISCUSSION: Methylphenidate reduced energy intake of a highly palatable food over one meal by one-third in obese adult males. Dopamine transport inhibition may be an effective component of a comprehensive treatment for obesity.     

Beta-oxidation of linoleate in obese men undergoing weight loss

BACKGROUND: In animals, the whole-body content and accumulation of linoleate can be measured and compared with its intake to determine linoleate beta-oxidation. This method can also provide quantitative information about the beta-oxidation of linoleate in humans. OBJECTIVES: The objectives of the study were to 1) use the wholebody fatty acid balance method to quantify whole-body concentrations of linoleate in humans, 2) estimate the distribution of linoleate between adipose and lean tissue, and 3) assess the effect of weight loss on linoleate stores and beta-oxidation in obese humans. DESIGN: Nine healthy obese men underwent supervised weight loss for 112 d (16 wk). Magnetic resonance imaging data and fatty acid profiles from fat biopsies were both used to determine linoleate stores in adipose and lean tissue and in the whole body. Linoleate beta-oxidation was calculated as intake - (accumulation + excretion). RESULTS: Mean weight loss was 13 kg and linoleate intake was 24 +/- 6 mmol/d over the study period. Whole-body loss of linoleate was 37 +/- 18 mmol/d, or 28% of the level before weight loss. Combining the intake and whole-body loss of linoleate resulted in linoleate beta-oxidation exceeding intake by 2.5-fold during the weight-loss period. CONCLUSIONS: All dietary linoleate is beta-oxidized and at least an equivalent amount of linoleate is lost from the body during moderate weight loss in obese men. The method studied permits the assessment of long-term changes in linoleate homeostasis in obese humans and may be useful in determining the risk of linoleate deficiency in other conditions.     

Consumption of a liquid high-fat meal increases triglycerides but decreases high-density lipoprotein cholesterol in abdominally obese subjects with high postprandial insulin resistance

Abdominal obesity is associated with an increased risk of insulin resistance, which may be a potential contributor to dyslipidemia. However, the relationship between postprandial insulin resistance and lipid metabolism in abdominally obese subjects remains unknown. We hypothesized that postprandial dyslipidemia would be exaggerated in abdominally obese subjects with high postprandial insulin resistance. To test this hypothesis, serum glucose, insulin, triglycerides, total cholesterol, high-density lipoprotein cholesterol, and apolipoprotein B were measured at baseline and postprandial state at 0.5, 1, 2, 4, 6, and 8 hours after a liquid high-fat meal in non–abdominally obese controls (n = 44) and abdominally obese subjects with low (AO-LPIR, n = 40), middle (n = 40), and high postprandial insulin resistance (AO-HPIR, n = 40) based on the tertiles ratio of the insulin to glucose areas under the curve (AUC). Their serum adipokines were tested at baseline only. Fasting serum leptin was higher (P < .05) in AO-HPIR than that in AO-LPIR and controls. Postprandial triglycerides AUC was higher (P < .05), whereas high-density lipoprotein cholesterol AUC was lower (P < .05), in AO-HPIR than those in AO-LPIR and controls. Postprandial AUCs for total cholesterol and apolipoprotein B were similar in abdominally obese subjects with different degrees of postprandial insulin resistance and controls. The present study indicated that the higher degree of postprandial insulin resistance, the more adverse lipid profiles in abdominally obese subjects, which provides insight into opportunity for screening in health.     

Psychosocial correlates of dietary intake among overweight and obese men

OBJECTIVES: To investigate the relationship between theoretically based psychosocial constructs and dietary components among overweight men. METHODS: Participants were 441 men (BMI M = 34.2). Psychosocial constructs included self-efficacy, decisional balance, social support, and behavior change strategies. Dietary components were fat, fiber, and fruit and vegetable intake. RESULTS: All significant findings were in the expected direction. Multiple regression models indicated that the psychosocial factors accounted for the most variance in vegetable intake (R(2)=.13) and the least variance in fat (R(2)=.05). CONCLUSIONS: Theoretically based psychosocial constructs were related to overweight men's dietary intake and have potential for use in tailored behavior-change interventions.