Endocrine and metabolic effects of consuming fructose- and glucose-sweetened beverages with meals in obese men and women: influence of insulin resistance on plasma triglyceride responses

CONTEXT

Compared with glucose-sweetened beverages, consumption of fructose-sweetened beverages with meals elevates postprandial plasma triglycerides and lowers 24-h insulin and leptin profiles in normal-weight women. The effects of fructose, compared with glucose, ingestion on metabolic profiles in obese subjects has not been studied.

OBJECTIVE

The objective of the study was to compare the effects of fructose- and glucose-sweetened beverages consumed with meals on hormones and metabolic substrates in obese subjects.

DESIGN AND SETTING

The study had a within-subject design conducted in the clinical and translational research center.

PARTICIPANTS

Participants included 17 obese men (n = 9) and women (n = 8), with a body mass index greater than 30 kg/m(2).

INTERVENTIONS

Subjects were studied under two conditions involving ingestion of mixed nutrient meals with either glucose-sweetened beverages or fructose-sweetened beverages. The beverages provided 30% of total kilocalories. Blood samples were collected over 24 h.

MAIN OUTCOME MEASURES

Area under the curve (24 h AUC) for glucose, lactate, insulin, leptin, ghrelin, uric acid, triglycerides (TGs), and free fatty acids was measured.

RESULTS

Compared with glucose-sweetened beverages, fructose consumption was associated with lower AUCs for insulin (1052.6 +/- 135.1 vs. 549.2 +/- 79.7 muU/ml per 23 h, P < 0.001) and leptin (151.9 +/- 22.7 vs. 107.0 +/- 15.0 ng/ml per 24 h, P < 0.03) and increased AUC for TG (242.3 +/- 96.8 vs. 704.3 +/- 124.4 mg/dl per 24 h, P < 0.0001). Insulin-resistant subjects exhibited larger 24-h TG profiles (P < 0.03).

CONCLUSIONS

In obese subjects, consumption of fructose-sweetened beverages with meals was associated with less insulin secretion, blunted diurnal leptin profiles, and increased postprandial TG concentrations compared with glucose consumption. Increases of TGs were augmented in obese subjects with insulin resistance, suggesting that fructose consumption may exacerbate an already adverse metabolic profile present in many obese subjects.

Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans

Studies in animals have documented that, compared with glucose, dietary fructose induces dyslipidemia and insulin resistance. To assess the relative effects of these dietary sugars during sustained consumption in humans, overweight and obese subjects consumed glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 weeks. Although both groups exhibited similar weight gain during the intervention, visceral adipose volume was significantly increased only in subjects consuming fructose. Fasting plasma triglyceride concentrations increased by approximately 10% during 10 weeks of glucose consumption but not after fructose consumption. In contrast, hepatic de novo lipogenesis (DNL) and the 23-hour postprandial triglyceride AUC were increased specifically during fructose consumption. Similarly, markers of altered lipid metabolism and lipoprotein remodeling, including fasting apoB, LDL, small dense LDL, oxidized LDL, and postprandial concentrations of remnant-like particle-triglyceride and -cholesterol significantly increased during fructose but not glucose consumption. In addition, fasting plasma glucose and insulin levels increased and insulin sensitivity decreased in subjects consuming fructose but not in those consuming glucose. These data suggest that dietary fructose specifically increases DNL, promotes dyslipidemia, decreases insulin sensitivity, and increases visceral adiposity in overweight/obese adults.

Less-energy-dense diets of low-income women in California are associated with higher energy-adjusted diet costs

BACKGROUND

US-based studies are needed to estimate the relation, if any, between diet quality and estimated diet costs.

OBJECTIVE

We hypothesized that lower cost diets among low-income women in California would be energy dense but nutrient poor.

DESIGN

Energy and nutrient intakes for 112 women aged 18-45 y living in California were obtained with a food-frequency instrument. Dietary energy density (in MJ/kg or kcal/g) and energy-adjusted diet costs (in $/10 MJ or $/2000 kcal) were calculated with local food prices. Tertile splits of energy density and energy cost were analyzed with one-factor analysis of variance.

RESULTS

Mean daily energy intake excluding all beverages was 7.1 MJ (1699 kcal), and mean dietary energy density was 6.5 kJ/kg (1.54 kcal/g). Lower dietary energy density was associated with significantly higher intakes of dietary fiber (P = 0.004), vitamin A (P < 0.001), and vitamin C (P < 0.001) and with significantly lower intakes of total fat (P = 0.003) and saturated fat (P < 0.001). Higher diet cost was associated with significantly lower dietary energy density (P < 0.001), total fat (P = 0.024), and saturated fat (P = 0.025) and with significantly higher intakes of vitamins A (P = 0.003) and C (P < 0.001). Each additional dollar in estimated diet costs was associated with a drop in energy density of 0.94 MJ/kg (0.225 kcal/g).

CONCLUSIONS

The finding that higher quality diets were more costly for these low-income women has implications for the food assistance and education programs of the US Department of Agriculture. Policy interventions may be required to allow low-income families in the United States to improve the quality of their diets given their food budget constraints.

Twenty-four-hour endocrine and metabolic profiles following consumption of high-fructose corn syrup-, sucrose-, fructose-, and glucose-sweetened beverages with meals

BACKGROUND

We have reported that, compared with glucose-sweetened beverages, consuming fructose-sweetened beverages with meals results in lower 24-h circulating glucose, insulin, and leptin concentrations and elevated triacylglycerol (TG). However, pure fructose and glucose are not commonly used as sweeteners. High-fructose corn syrup (HFCS) has replaced sucrose as the predominant sweetener in beverages in the United States.

OBJECTIVE

We compared the metabolic/endocrine effects of HFCS with sucrose and, in a subset of subjects, with pure fructose and glucose.

DESIGN

Thirty-four men and women consumed 3 isocaloric meals with either sucrose- or HFCS-sweetened beverages, and blood samples were collected over 24 h. Eight of the male subjects were also studied when fructose- or glucose-sweetened beverages were consumed.

RESULTS

In 34 subjects, 24-h glucose, insulin, leptin, ghrelin, and TG profiles were similar between days that sucrose or HFCS was consumed. Postprandial TG excursions after HFCS or sucrose were larger in men than in women. In the men in whom the effects of 4 sweeteners were compared, the 24-h glucose and insulin responses induced by HFCS and sucrose were intermediate between the lower responses during consumption of fructose and the higher responses during glucose. Unexpectedly, postprandial TG profiles after HFCS or sucrose were not intermediate but comparably high as after pure fructose.

CONCLUSIONS

Sucrose and HFCS do not have substantially different short-term endocrine/metabolic effects. In male subjects, short-term consumption of sucrose and HFCS resulted in postprandial TG responses comparable to those induced by fructose.

High-selenium yeast supplementation in free-living North American men: no effect on thyroid hormone metabolism or body composition

In a prior study, we observed decreased serum 3,3',5-triiodothyronine (T(3)), increased serum thyrotropin and increased body weight in five men fed 297 microg/d of selenium (Se) in foods naturally high in Se while confined in a metabolic research unit. In an attempt to replicate and confirm those observations, we conducted a randomized study of high-Se yeast supplements (300 microg/d) or placebo yeast administered to 42 healthy free-living men for 48 weeks. Serum thyroxine, T(3) and thyrotropin did not change in supplemented or control subjects. Body weight increased in both groups during the 48-week treatment period and remained elevated for the 48-week follow-up period. Body fat increased by 1.2 kg in both groups. Energy intake and voluntary activity levels were not different between the groups and remained unchanged during the treatment period. Dietary intakes of Se, macronutrients and micronutrients were not different between groups and remained unchanged during the treatment period. These results suggest that our previous observation of a hypothyroidal response to high-Se foods was confounded by some aspect of the particular foods used, or were merely chance observations. Because of the high dose and long administration period, the present study suggests that the effects of Se supplements on thyroid hormone metabolism and energy metabolism in healthy North American men with adequate Se status do not represent a significant risk for unhealthy weight gain.

Raman spectroscopic analysis of biochemical changes in individual triglyceride-rich lipoproteins in the pre- and postprandial state

Individual triglyceride-rich lipoprotein (TGRL) particles derived from human volunteers are nondestructively analyzed by laser tweezers Raman microspectroscopy, and information on their composition and distribution is obtained. The Raman signature of single optically trapped very low-density lipoproteins (VLDL), a subclass of TGRL, which play an important role in cardiovascular disease, exhibits distinct peaks associated with molecular vibrations of fatty acids, proteins, lipids, and structural rearrangements of lipids. Our analysis of pre- and postprandial VLDL exhibits the signature of biochemical changes in individual lipoprotein particles following the consumption of meals. Interaction of VLDL with endothelium leads to the breakdown of complex triacylglycerols and the formation of a highly ordered core of free saturated fatty acids in the particle. A particle distribution analysis reveals trends in the degree to which this process has occurred in particles at different times during the postprandial period. Differences in particle distributions based on the different ratios of polyunsaturated to saturated fats in the consumed meals are also easily discerned. Individual lipoprotein particles hydrolyzed in vitro through addition of lipoprotein lipase (LpL) exhibit strikingly similar changes in their Raman spectra. These results demonstrate the feasibility of monitoring the dynamics of lipid metabolism of individual TGRL particles as they interact with LpL in the endothelial cell wall using Raman spectroscopy.

Postprandial monocyte activation in response to meals with high and low glycemic loads in overweight women

BACKGROUND

Recent data show that atherosclerosis is initiated and perpetuated by inflammatory events. Activation of immune cells such as monocytes initiates inflammation, a key step in atherosclerosis.

OBJECTIVE

We hypothesize that a high-glycemic load meal activates inflammatory cells, and that this is mediated by elevated circulating triacylglycerol-rich lipoproteins.

DESIGN

Sixteen women [body mass index (in kg/m2): 25.7-29.6], aged 20-48 y, consumed meals with a high or a low glycemic load in a crossover fashion. Blood samples were collected before and up to 8 h after the meals. Samples were measured for glucose, insulin, triacylglycerols, and circulating cytokines, and expression of tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) was measured by flow cytometry.

RESULTS

At 3.5 h after the test meals, we observed a significant increase in monocytes expressing TNF-alpha with both high-and low-glycemic load meals. Also, expression of IL-1beta in monocytes tended to increase, but the change was not significant. The glycemic load of the meal did not influence circulating cytokines and had only a minimal effect on postprandial triacylglycerol concentrations despite marked postprandial changes in glycemia and circulating insulin concentrations.

CONCLUSIONS

In the postprandial state, monocytes can be activated by both high-and low-glycemic load meals. The glycemic load of a single meal did not have a significant effect on the degree of activation of the monocytes in women who displayed only a modest increase in circulating triacylglycerols in response to test meals. Future studies should examine the effect of glycemic load in subjects who have a hyperlipemic response to dietary carbohydrate.

Size Acceptance and Intuitive Eating Improve Health for Obese, Female Chronic Dieters

OBJECTIVE

Examine a model that encourages health at every size as opposed to weight loss. The health at every size concept supports homeostatic regulation and eating intuitively (ie, in response to internal cues of hunger, satiety, and appetite).

DESIGN

Six-month, randomized clinical trial; 2-year follow-up.

SUBJECTS

White, obese, female chronic dieters, aged 30 to 45 years (N=78).

SETTING

Free-living, general community.

INTERVENTIONS

Six months of weekly group intervention (health at every size program or diet program), followed by 6 months of monthly aftercare group support.

MAIN OUTCOME MEASURES

Anthropometry (weight, body mass index), metabolic fitness (blood pressure, blood lipids), energy expenditure, eating behavior (restraint, eating disorder pathology), and psychology (self-esteem, depression, body image). Attrition, attendance, and participant evaluations of treatment helpfulness were also monitored.

STATISTICAL ANALYSIS PERFORMED

Analysis of variance.

RESULTS

Cognitive restraint decreased in the health at every size group and increased in the diet group, indicating that both groups implemented their programs. Attrition (6 months) was high in the diet group (41%), compared with 8% in the health at every size group. Fifty percent of both groups returned for 2-year evaluation. Health at every size group members maintained weight, improved in all outcome variables, and sustained improvements. Diet group participants lost weight and showed initial improvement in many variables at 1 year; weight was regained and little improvement was sustained.

CONCLUSIONS

The health at every size approach enabled participants to maintain long-term behavior change; the diet approach did not. Encouraging size acceptance, reduction in dieting behavior, and heightened awareness and response to body signals resulted in improved health risk indicators for obese women.

America's obesity epidemic: measuring physical activity to promote an active lifestyle

The incidence of overweight and obesity in the United States and worldwide has reached epidemic proportions. To effectively intervene, dietetics professionals and other health care practitioners need to address both sides of the energy balance equation when counseling clients and patients. Often, the focus on energy intake supersedes the promotion of a physically active lifestyle. Incorporating appropriate and sufficient physical activity into one's life is an essential component of achieving and maintaining a healthful body weight. This review summarizes background knowledge on the benefits of physical activity for health and provides an overview of available tools for measuring physical activity and energy expenditure. The physical and mental health benefits of an active lifestyle, current physical activity recommendations for the US public, the prevalence of inactivity in the United States, and components of energy expenditure are reviewed. Additionally, tools for estimating total energy expenditure, resting metabolic rate, and physical activity are evaluated and suitable approaches for applying these tools are provided.

Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women

Previous studies indicate that leptin secretion is regulated by insulin-mediated glucose metabolism. Because fructose, unlike glucose, does not stimulate insulin secretion, we hypothesized that meals high in fructose would result in lower leptin concentrations than meals containing the same amount of glucose. Blood samples were collected every 30-60 min for 24 h from 12 normal-weight women on 2 randomized days during which the subjects consumed three meals containing 55, 30, and 15% of total kilocalories as carbohydrate, fat, and protein, respectively, with 30% of kilocalories as either a fructose-sweetened [high fructose (HFr)] or glucose-sweetened [high glucose (HGl)] beverage. Meals were isocaloric in the two treatments. Postprandial glycemic excursions were reduced by 66 +/- 12%, and insulin responses were 65 +/- 5% lower (both P < 0.001) during HFr consumption. The area under the curve for leptin during the first 12 h (-33 +/- 7%; P < 0.005), the entire 24 h (-21 +/- 8%; P < 0.02), and the diurnal amplitude (peak - nadir) (24 +/- 6%; P < 0.0025) were reduced on the HFr day compared with the HGl day. In addition, circulating levels of the orexigenic gastroenteric hormone, ghrelin, were suppressed by approximately 30% 1-2 h after ingestion of each HGl meal (P < 0.01), but postprandial suppression of ghrelin was significantly less pronounced after HFr meals (P < 0.05 vs. HGl). Consumption of HFr meals produced a rapid and prolonged elevation of plasma triglycerides compared with the HGl day (P < 0.005). Because insulin and leptin, and possibly ghrelin, function as key signals to the central nervous system in the long-term regulation of energy balance, decreases of circulating insulin and leptin and increased ghrelin concentrations, as demonstrated in this study, could lead to increased caloric intake and ultimately contribute to weight gain and obesity during chronic consumption of diets high in fructose.

Low bone mass in premenopausal chronic dieting obese women

BACKGROUND

Obese premenopausal women are thought to be at low risk for osteoporosis due to increased body weight and effects of estrogen on weight-bearing bone.

OBJECTIVE

To examine the effect of restrained eating on obese women, we examined bone mineral density (BMD) and content (BMC) of the spine and femur in obese women who were restrained eaters, with emphasis on the relationship between BMC and determinants of bone mass, and current eating behaviors, dietary intake, physical activity, and indices of calcium regulation, bone metabolism, stress and inflammation.

DESIGN

A total of 78 obese, Caucasian, female, restrained eaters, ages 30-45 y, were enrolled in a weight lose program. Height, weight, bone turnover markers, serum parathyroid hormone (PTH), cortisol, c-reactive protein (CRP), dietary intake, eating behaviors, physical activity, and BMD and BMC were measured.

SETTING

This study was conducted at the University of California, in Davis, CA, USA.

RESULTS

In all, 31% of women had osteopenia or osteoporosis (OSTEO). In the OSTEO group, 87.5% of women had osteoporosis or osteopenia of the lumbar spine and 12.5% of the women had osteoporosis or osteopenia in femur. A significant positive correlation between BMC and energy expenditure (r=0.256), and a significant negative correlation between BMC and number of times on a weight loss diet (r=-0.250) and cognitive restraint (r=-0.239) were observed. No significant differences were observed between OSTEO women and nonosteoporotic women for current eating behaviors, dietary intake, physical activity habits, bone turnover, calcium regulation, stress, or inflammation.

CONCLUSIONS

Obese restrained eaters are at risk for low bone mass. Prior dieting may be responsible. Chronic dieters should be encouraged to decrease their dietary restraint, develop healthy eating habits and increase physical activity.

Restrained eating behavior and the metabolic response to dietary energy restriction in women

OBJECTIVE

To determine whether prior eating behavior characterized by dietary restraint alters responses in energy expenditure and substrate oxidation associated with a short-term, energy-restricted diet.

RESEARCH METHODS AND PROCEDURES

A repeated-measures, 3-day diet-intervention study of adequate (125 kJ/kg of body weight) or restricted (62.5 kJ/kg) energy intake was conducted with 30 women, 20 to 46 years, BMI 25 to 45 kg/m(2), whose prior eating behavior was "restrained" or "unrestrained." The Eating Inventory (cognitive restraint subscale) was used to measure restrained eating behavior. Energy expenditure and substrate oxidation were measured after a 12-hour fast and during the first and fourth hours after a standard meal. Plasma glucose, nonesterified fatty acids, and insulin were measured at corresponding times. Body composition was determined by total body electrical conductivity.

RESULTS

Resting energy expenditure was not affected by 3 days of energy restriction. Short-term energy restriction resulted in lower respiratory-exchange ratios, higher rates of fat oxidation, and lower rates of carbohydrate oxidation. Subjects classified as restrained eaters had higher postprandial respiratory-exchange ratios and carbohydrate-oxidation rates compared with unrestrained eaters. Fasting insulin concentrations were lower in restrained eaters. These effects associated with prior eating behavior were independent of the diet intervention.

DISCUSSION

Metabolic outcomes associated with a 3-day energy-restricted diet (i.e., increased fat oxidation and decreased carbohydrate oxidation) were not affected by prior restrained eating behavior. However, restrained eating behavior was associated with increased carbohydrate oxidation after a mixed meal. This effect of restrained eating behavior may be attributable to increased insulin sensitivity.