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/m², 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.     

Physical Activity and Low-Fat Diet: Is it Enough to Maintain Weight Stability in the Reduced-Obese Individual Following Weight Loss by Drug Therapy and Energy Restriction?

DOUCET, ERIC, PASCAL IMBEAULT, NATALIE ALMÉRAS, AND ANGELO TREMBLAY. Physical activity and low-fat diet: Is it enough to maintain weight stability in the reduced-obese individual following weight loss by drug therapy and energy restriction? Obes Res. Objective: The anthropometric and physiological effects of a physical activity (PA) and a mildly energy-restricted low-fat diet (LFD) follow-up program after a long-term dietary restriction were studied in 12 men and 8 women. Research Methods and Procedures: The dietary restriction (?700 kcal/day) was accompanied by a fenfluramine (60 mg/day) or placebo treatment for 15 weeks, whereas the mean duration of the PA-LFD follow-up was 18 weeks. Results: The long-term dietary restriction reduced body weight (?11. 9 and ?7. 6 kg, p<. 001), fat mass (FM) (?10. 6 and ?5. 8 kg, p<0. 01), resting metabolic rate (RMR) (?304 kcal/day, p<0. 01 and ?148 kcal/day, NS) in men and women, respectively. A decrease in fat-free mass (FFM) was also observed in women (?1. 8 kg, p<0. 05). The PA-LFD follow-up preserved weight stability at a reduced body weight and caused an additional significant decrease in FM for men (?3. 4 kg, p<0. 05). This part of the intervention also caused an increase in daily RMR for men (134 kcal/day, NS) to the point where this value no longer differed from the pre-energy restriction value. In contrast, RMR was further reduced in women (?200 kcal/day) to the point where it Significantly differed from initial values (p<0. 01). Resting seated heart rate was reduced by the PA-LFD follow-up in men leading it to differ significantly from both pre- and post-energy restriction values (?8. 5 and ?5. 5 bpm, p<0. 01). Discussion: In conclusion, these results suggest that a PA-LFD follow-up has the potential to permit body weight stability and may even accentuate fat loss in the reduced-obese state. Moreover, resting energy expenditure is increased under such conditions in men. These stimulating effects seem to be specific to energy metabolism since seated heart rate was either further reduced or remained stable in response to the PA-LFD follow-up.     

Effects of dietary fat content on adiposity during energy restriction in genetically obese rats.

The effects of the amount of fat provided in a restricted diet on weight loss and body composition were studied in this work. Lean male (Fa/?) Zucker rats were fed a control diet ad libitum. Obese (fa/fa) Zucker rats were divided into three groups: one group was fed a control diet ad libitum and the other two groups were fed 75% energy-restricted diets, which provided 10 or 50% of calories as fat. After 4 weeks, energy restriction normalized body weight but not body composition in the genetically obese rats. Reductions in adipose tissue weights and adipocyte size, without changes in the cellularity, were observed. Differences only reached statistical significance in subcutaneous adipose tissue. A standard fat content in the diet induced the same fat-free mass reduction as a higher amount of this macronutrient, but a greater body fat reduction. This suggests that the restriction of dietary fat, as well as energy, is necessary to achieve dietary management in obesity.     

Calcium and Dairy Acceleration of Weight and Fat Loss during Energy Restriction in Obese Adults

Objective: Increasing 1, 25‐dihydroxyvitamin D in response to low‐calcium diets stimulates adipocyte Ca²⁺ influx and, as a consequence, stimulates lipogenesis, suppresses lipolysis, and increases lipid accumulation, whereas increasing dietary calcium inhibits these effects and markedly accelerates fat loss in mice subjected to caloric restriction. Our objective was to determine the effects of increasing dietary calcium in the face of caloric restriction in humans. Research Methods and Procedures: We performed a randomized, placebo‐controlled trial in 32 obese adults. Patients were maintained for 24 weeks on balanced deficit diets (500 kcal/d deficit) and randomized to a standard diet (400 to 500 mg of dietary calcium/d supplemented with placebo), a high‐calcium diet (standard diet supplemented with 800 mg of calcium/d), or high‐dairy diet (1200 to 1300 mg of dietary calcium/d supplemented with placebo). Results: Patients assigned to the standard diet lost 6.4 ± 2.5% of their body weight, which was increased by 26% (to 8.6 ± 1.1%) on the high‐calcium diet and 70% (to 10.9 ± 1.6% of body weight) on the high‐dairy diet (p < 0.01). Fat loss was similarly augmented by the high‐calcium and high‐dairy diets, by 38% and 64%, respectively (p < 0.01). Moreover, fat loss from the trunk region represented 19.0 ± 7.9% of total fat loss on the low‐calcium diet, and this fraction was increased to 50.1 ± 6.4% and 66.2 ± 3.0% on the high‐calcium and high‐dairy diets, respectively (p < 0.001). Discussion: Increasing dietary calcium significantly augmented weight and fat loss secondary to caloric restriction and increased the percentage of fat lost from the trunk region, whereas dairy products exerted a substantially greater effect.     

Contribution of Different Mechanisms to Compensation for Energy Restriction in the Mouse

Objective: Restriction of energy intake produces weight loss, but the rate of loss is seldom sustained. This is presumed to be a consequence of compensatory reductions in energy expenditure, although the exact contributions of different components to the energy budget remain uncertain. We examined the compensatory responses of mice to a 20% dietary restriction. Research Methods and Procedures: We measured body mass, body fatness, body temperature, and the components of daily energy expenditure for 50 MF1 mice. Forty mice were then placed on a restricted diet at 80% of their ad libitum intake for 50 days. The remaining 10 mice continued to feed ad libitum. Ten days before the end of the restriction period, the same measurements were taken. Results: There were no significant differences between the control and restricted groups in any parameters before restriction. During the restriction period, body mass increased in both the control and restricted groups, but at a slower rate in the restricted mice. The control group increased in both fat and fat free mass; however, although the restricted group increased fat to the same extent as the controls, fat free mass increased to a lesser extent. The contributions of the different components of the expended energy to compensate for the reduced energy intake were energy deposition, 2.2%; resting metabolic rate, 22.3%; and activity, 75.5%. Discussion: Mice were able to compensate almost completely for the restricted energy intake that was achieved by altering the amount of energy required for each component of the energy budget except digestive efficiency.     

Intermittent Moderate Energy Restriction Improves Weight Loss Efficiency in Diet-Induced Obese Mice

Background

Intermittent severe energy restriction is popular for weight management. To investigate whether intermittent moderate energy restriction may improve this approach by enhancing weight loss efficiency, we conducted a study in mice, where energy intake can be controlled.

Methods

Male C57/Bl6 mice that had been rendered obese by an ad libitum diet high in fat and sugar for 22 weeks were then fed one of two energy-restricted normal chow diets for a 12-week weight loss phase. The continuous diet (CD) provided 82% of the energy intake of age-matched ad libitum chow-fed controls. The intermittent diet (ID) provided cycles of 82% of control intake for 5–6 consecutive days, and ad libitum intake for 1–3 days. Weight loss efficiency during this phase was calculated as (total weight change) ÷ [(total energy intake of mice on CD or ID)–(total average energy intake of controls)]. Subsets of mice then underwent a 3-week weight regain phase involving ad libitum re-feeding.

Results

Mice on the ID showed transient hyperphagia relative to controls during each 1–3-day ad libitum feeding period, and overall ate significantly more than CD mice (91.1±1.0 versus 82.2±0.5% of control intake respectively, n = 10, P<0.05). There were no significant differences between CD and ID groups at the end of the weight loss or weight regain phases with respect to body weight, fat mass, circulating glucose or insulin concentrations, or the insulin resistance index. Weight loss efficiency was significantly greater with ID than with CD (0.042±0.007 versus 0.018±0.001 g/kJ, n = 10, P<0.01). Mice on the CD exhibited significantly greater hypothalamic mRNA expression of proopiomelanocortin (POMC) relative to ID and control mice, with no differences in neuropeptide Y or agouti-related peptide mRNA expression between energy-restricted groups.

Conclusion

Intermittent moderate energy restriction may offer an advantage over continuous moderate energy restriction, because it induces significantly greater weight loss relative to energy deficit in mice.     

Temporal pattern of eating in night shift workers

ABSTRACT

Understanding shift workers dietary intake patterns may inform interventions targeted at lowering chronic disease risk. This study examined the temporal distribution of food intake as shift workers rotate between night shifts, day shift and/or days off to identify differences in energy intake, eating frequency, and adherence to dietary guidelines by shift type (night shift vs. day). Night shift (NS) workers completed a four-day food diary that included a minimum of two night shifts and one-day shift (DS)/day off (DO), recording all food, beverages and time of consumption. Comparisons were between shift types, using ANOVA for continuous data and generalized estimating equations for count data, data reported as mean (SE). When comparing NS and DSDO, there were no differences in energy intake (24 h) (8853 (702) vs. 9041 (605) kJ, n = 22) or adherence to dietary guidelines. There was no difference between the number of eating occasions on NS and DSDO (5.6(0.3) vs 5.1(0.6) occasions) but less energy per eating occasion at night (1661(125) vs 1933(159) kJ). When working NS compared with DSDO there was higher total sugar (%E, 19.1(2.0) vs 15.0(2.4)) and lower saturated fat (%E, 13.8(1.2) vs 15.7(1.3)). Further, DSDO were characterized by a pattern of three main meals and a prolonged fasting period. It is important to determine if reducing eating occasions and providing opportunities for fasting improves metabolic health.     

Effects of Calcium and Dairy on Body Composition and Weight Loss in African‐American Adults

Objective: Our objective was to determine the effects of dairy consumption on adiposity and body composition in obese African Americans. Research Methods and Procedures: We performed two randomized trials in obese African‐American adults. In the first (weight maintenance), 34 subjects were maintained on a low calcium (500 mg/d)/low dairy (<1 serving/d) or high dairy (1200 mg Ca/d diet including 3 servings of dairy) diet with no change in energy or macronutrient intake for 24 weeks. In the second trial (weight loss), 29 subjects were similarly randomized to the low or high dairy diets and placed on a caloric restriction regimen (?500 kcal/d). Results: In the first trial, body weight remained stable for both groups throughout the maintenance study. The high dairy diet resulted in decreases in total body fat (2.16 kg, p < 0.01), trunk fat (1.03 kg, p < 0.01), insulin (18.7 pM, p < 0.04), and blood pressure (6.8 mm Hg systolic, p < 0.01; 4.25 mm Hg diastolic, p < 0.01) and an increase in lean mass (1.08 kg, p < 0.04), whereas there were no significant changes in the low dairy group. In the second trial, although both diets produced significant weight and fat loss, weight and fat loss on the high dairy diet were ～2‐fold higher (p < 0.01), and loss of lean body mass was markedly reduced (p < 0.001) compared with the low dairy diet. Discussion: Substitution of calcium‐rich foods in isocaloric diets reduced adiposity and improved metabolic profiles in obese African Americans without energy restriction or weight loss and augmented weight and fat loss secondary to energy restriction.     

The Effects of Consuming Frequent,Higher Protein Meals on Appetite and Satiety During Weight Loss in Overweight/Obese Men

The purpose of this study was to determine the effects of dietary protein and eating frequency on perceived appetite and satiety during weight loss. A total of 27 overweight/obese men (age 47 ± 3 years; BMI 31.5 ± 0.7 kg/m²) were randomized to groups that consumed an energy‐restriction diet (i.e., 750 kcal/day below daily energy need) as either higher protein (HP, 25% of energy as protein, n = 14) or normal protein (NP, 14% of energy as protein, n = 13) for 12 weeks. Beginning on week 7, the participants consumed their respective diets as either 3 eating occasions/day (3‐EO; every 5 h) or 6 eating occasions/day (6‐EO; every 2 h), in randomized order, for 3 consecutive days. Indexes of appetite and satiety were assessed every waking hour on the third day of each pattern. Daily hunger, desire to eat, and preoccupation with thoughts of food were not different between groups. The HP group experienced greater fullness throughout the day vs. NP (511 ± 56 vs. 243 ± 54 mm · 15 h; P < 0.005). When compared to NP, the HP group experienced lower late‐night desire to eat (13 ± 4 vs. 27 ± 4 mm, P < 0.01) and preoccupation with thoughts of food (8 ± 4 vs. 21 ± 4 mm; P < 0.01). Within groups, the 3 vs. 6‐EO patterns did not influence daily hunger, fullness, desire to eat, or preoccupation with thoughts of food. The 3‐EO pattern led to greater evening and late‐night fullness vs. 6‐EO but only within the HP group (P < 0.005). Collectively, these data support the consumption of HP intake, but not greater eating frequency, for improved appetite control and satiety in overweight/obese men during energy restriction‐induced weight loss.     

Effect of Age on Protein Conservation during Very-Low-Energy Diet in Obese Sprague-Dawley Rats

JOHNSON, JULIA A, CHOON-HIE YU, MEI-UIH YANG, F. XAVIER PI-SUNYER. Effect of age on protein conservation during very-low-energy diet in obese Sprague-Dawley rats. Obes. Res. 1998;6:448-157. Objective : To examine the effect of age on body protein losses occurring during severe energy restriction in obesity. Research Methods and Procedures : Weanling (young) Sprague-Dawley rats (YR) were fed a high fat (35% energy) diet (HFD) until mean body weight approached that of a group of chowfed retired breeder (aged) rats (AR). Both groups were then fed HFD for an additional 2 weeks, after which selected controls from YR and AR groups were killed for baseline carcass analysis. Remaining rats were fed a very-low-energy diet (VLED, 33% kcal of HFD) for 3 weeks and then killed for carcass analysis. Results : YR had greater fat stores before VLED, and lost proportionately more fat and less protein during VLED than did AR. Weight loss composition during VLED was 66.7% fat, 11.1% protein, and 22.2% water in YR, and 39.4% fat, 26.2% protein, and 34.3% water in AR. Greater YR fat loss during VLED* (70.6 ± 30.4 vs. 32.6 ± 29.1 g in AR; mean ± SD) was paralleled by significantly larger decreases in epididymal and retroperitoneal fat pad weights, mean adipocyte size, and lipoprotein lipase activity. Greater protein loss in AR (21.6 ± 13.9 g vs. 11.8 ± 10.7 g in YR) coincided with larger decreases in visceral organ weights and serum thyroxine and triiodothyronine. Energy expenditure changes during VLED were similar between groups. Discussion : Dietary obese young rats appear better able than aged rats to conserve body protein while losing body fat during severe energy restriction.     

Adipose tissue metabolism and inflammation are differently affected by weight loss in obese mice due to either a high-fat diet restriction or change to a low-fat diet

Restriction of a high-fat diet (HFD) and a change to a low-fat diet (LFD) are two interventions that were shown to promote weight loss and improve parameters of metabolic health in obesity. Examination of the biochemical and molecular responses of white adipose tissue (WAT) to these interventions has not been performed so far. Here, male C57BL/6JOlaHsd mice, harboring an intact nicotinamide nucleotide transhydrogenase gene, were fed a purified 40 energy% HFD for 14 weeks to induce obesity. Afterward, mice were divided into three dietary groups: HFD (maintained on HFD), LFD (changed to LFD with identical ingredients), and HFD-CR (restricted to 70 % of the HFD). The effects of the interventions were examined after 5 weeks. Beneficial effects were seen for both HFD-CR and LFD (compared to HFD) regarding physiological parameters (body weight and fat mass) and metabolic parameters, including circulating insulin and leptin levels. Macrophage infiltration in WAT was reduced by both interventions, although more effectively by HFD-CR. Strikingly, molecular parameters in WAT differed between HFD-CR and LFD, with increased activation of mitochondrial carbohydrate and fat metabolism in HFD-CR mice. Our results confirm that restriction of the amount of dietary intake and reduction in the dietary energy content are both effective in inducing weight loss. The larger decrease in WAT inflammation and increase in mitochondrial carbohydrate metabolism may be due to a larger degree of energy restriction in HFD-CR, but could also be due to superior effectiveness of dietary restriction in weight loss strategies.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-014-0391-9) contains supplementary material, which is available to authorized users.     

Metabolic Fitness in Active Reduced-Obese Individuals

TREMBLAY, ANGELO, ERIC DOUCET, PASCAL IMBEAULT, PASCALE MAURIÈGE, JEAN-PIERRE DESPRÉS, AND DENIS RICHARD. Metabolic fitness in active reduced-obese individuals. Obes Res. Objective: To verify whether a physical activity-low-fat diet follow-up could normalize the metabolic risk profile of reduced-obese men and women having undergone considerable weight loss through energy restriction and drug therapy. Research Methods and Procedures: Twenty obese individuals (12 men, 8 women) participated in a weight-reducing program that included two phases. In the first phase, a non-macronutrient-specific dietary restriction of about 700 kcal/day was prescribed to induce weight loss over 15 weeks, with either fenfluramine or placebo. The second phase consisted of a physical activity-low-fat diet follow-up that was maintained as long as subjects did not experience resistance to further body weight and fat loss. Resistance to lose fat occurred after a mean cumulative fat loss of 14 and 8 kg in men and women, respectively. Results: Despite this substantial decrease in body fat, subjects' adiposity remained much higher at the end of this protocol than values observed in lean control subjects. However, fasting plasma levels of insulin, cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, and triglyceride as well as the response of insulin and glucose to oral glucose were normalized at the end of the physical activity-low-fat diet follow-up. Discussion: These results indicate that further weight and fat losses may not be justified when a moderate body weight loss resulting in a highly favorable improvement of metabolic risk profile is achieved in patients who would have still been diagnosed as overweight or obese on the basis of criteria currently promoted by public health agencies.     

Higher protein intake preserves lean mass and satiety with weight loss in pre-obese and obese women

Objective: To examine the effects of dietary protein and obesity classification on energy‐restriction‐induced changes in weight, body composition, appetite, mood, and cardiovascular and kidney health. Research Methods and Procedures: Forty‐six women, ages 28 to 80, BMI 26 to 37 kg/m², followed a 12‐week 750‐kcal/d energy‐deficit diet containing higher protein (HP, 30% protein) or normal protein (NP, 18% protein) and were retrospectively subgrouped according to obesity classification [pre‐obese (POB), BMI = 26 to 29.9 kg/m²; obese (OB), BMI = 30 to 37 kg/m²). Results: All subjects lost weight, fat mass, and lean body mass (LBM; p < 0.001). With comparable weight loss, LBM losses were less in HP vs. NP (?1.5 ± 0.3 vs. ?2.8 ± 0.5 kg; p < 0.05) and POB vs. OB (?1.2 ± 0.3 vs. ?2.9 ± 0.4 kg; p < 0.005). The main effects of protein and obesity on LBM changes were independent and additive; POB‐HP lost less LBM vs. OB‐NP (p < 0.05). The energy‐restriction‐induced decline in satiety was less pronounced in HP vs. NP (p < 0.005). Perceived pleasure increased with HP and decreased with NP (p < 0.05). Lipid‐lipoprotein profile and blood pressure improved and kidney function minimally changed with energy restriction (p < 0.05), independently of protein intake. Discussion: Consuming a higher‐protein diet and accomplishing weight loss before becoming obese help women preserve LBM. Use of a higher‐protein diet also improves perceptions of satiety and pleasure during energy restriction.     

Altered Brown Adipose Tissue and Na,K Pump Activities During Diet-Induced Obesity and Weight Loss in Rats

Brown adipose tissue (BAT) thermogenesis is an uncoupled ATPase-independent thermogenic mechanism. Ion transport by the Na,K pump is an ATPase- dependent thermogenic mechanism. Both have been proposed as mechanisms of altered energy expenditure during states of dietary energy surfeit and deficit. Our aim was to study these mechanisms during diet-induced obesity and weight loss. Over 36 weeks rats were fed lard- or tallow-based diets (63% energy as fat), or a control diet (12% energy as fat). During periods of restriction rats were fed 50% of the energy intake of controls in the form of a control diet. Several components of thermogenic response increased in rats eating high fat diets and decreased following dietary restriction. BAT activation occurred, particularly with a lard-based diet, as indicated by increased GDP binding and uncoupling protein (UCP) content. Na,K pump activity in thymocytes increased with the feeding of both high fat diets at some time points. Plasma T₃ level increased in rats eating the lard-based diet and decreased with dietary restriction regardless of previous diet. Resting metabolic rate (RMR) of the animals was unchanged despite increases in these thermogenic components and was decreased in all groups following dietary restriction. Our results indicate a lack of any major role for activated BAT thermogenesis in mitigating the extent of the obesity induced by the high fat diets. The reasons for the differences in response to the two different sources of saturated fat, lard, and tallow, are not clear.     

The Effect of Electronic Self‐Monitoring on Weight Loss and Dietary Intake: A Randomized Behavioral Weight Loss Trial

Technology may improve self‐monitoring adherence and dietary changes in weight loss treatment. Our study aimed to investigate whether using a personal digital assistant (PDA) with dietary and exercise software, with and without a feedback message, compared to using a paper diary/record (PR), results in greater weight loss and improved self‐monitoring adherence. Healthy adults (N = 210) with a mean BMI of 34.01 kg/m² were randomized to one of three self‐monitoring approaches: PR (n = 72), PDA with self‐monitoring software (n = 68), or PDA with self‐monitoring software and daily feedback messages (PDA+FB, n = 70). All participants received standard behavioral treatment. Self‐monitoring adherence and change in body weight, waist circumference, and diet were assessed at 6 months; retention was 91%. All participants had a significant weight loss (P < 0.01) but weight loss did not differ among groups. A higher proportion of PDA+FB participants (63%) achieved ≥5% weight loss in comparison to the PR group (46%) (P < 0.05) and PDA group (49%) (P = 0.09). Median percent self‐monitoring adherence over the 6 months was higher in the PDA groups (PDA 80%; PDA+FB 90%) than in the PR group (55%) (P < 0.01). Waist circumference decreased more in the PDA groups than the PR group (P = 0.02). Similarly, the PDA groups reduced energy and saturated fat intake more than the PR group (P < 0.05). Self‐monitoring adherence was greater in the PDA groups with the greatest weight change observed in the PDA+FB group.     

Effect of Dietary Carbohydrate Source on the Development of Obesity in Agouti Transgenic Mice**

Objectives: Our objective was to evaluate the effects of a qualitative change in dietary carbohydrate source on body weight and adiposity in a rodent model of diet‐induced obesity. Research Methods and Procedures: We evaluated the effects of high‐fat diets (basal) varying in carbohydrate source in aP2‐agouti transgenic mice. In the ad libitum study, animals were given free access to the basal diet or one of four test diets for 6 weeks. In two of the diets, dietary carbohydrate was derived from a single source: mung bean noodles (MUNG) or rolled oats (ROLL). The remaining diets were designed to mimic commercially available instant oatmeal with added sugar (IO‐S) or flavored instant oatmeal (IO‐F). In the energy‐restricted study, animals were given ad libitum access to the basal diet for 6 weeks. Subsequently, animals were assigned to one of six treatment groups for 6 weeks. One group was continued on the basal diet ad libitum. The remaining groups were maintained with energy restriction (70% ad libitum) on either the basal, MUNG, ROLL, IO‐S, or IO‐F diet. Results: Subcutaneous fat pad mass was significantly higher (p < 0.05) in the energy‐restricted basal and IO‐S groups compared with the energy‐restricted ROLL diet. Similarly, visceral fat pad mass was significantly lower with ROLL and MUNG diets (p < 0.05 for both) compared with basal and IO‐S diets, and the insulin:glucose ratio was reduced (by 23% to 34%, p < 0.05) in these two diets compared with all others. In ad libitum‐fed animals, liver fatty acid synthase expression was 43% to 62% lower (p < 0.05) with ROLL and MUNG diets compared with all others. Discussion: These data suggest that a qualitative change in dietary carbohydrate source modulates body weight and adiposity.     

Medium‐Chain Triglycerides Increase Energy Expenditure and Decrease Adiposity in Overweight Men

Objective: The objectives of this study were to compare the effects of diets rich in medium‐chain triglycerides (MCTs) or long‐chain triglycerides (LCTs) on body composition, energy expenditure, substrate oxidation, subjective appetite, and ad libitum energy intake in overweight men. Research Methods and Procedures: Twenty‐four healthy, overweight men with body mass indexes between 25 and 31 kg/m² consumed diets rich in MCT or LCT for 28 days each in a crossover randomized controlled trial. At baseline and after 4 weeks of each dietary intervention, energy expenditure was measured using indirect calorimetry, and body composition was analyzed using magnetic resonance imaging. Results: Upper body adipose tissue (AT) decreased to a greater extent (p < 0.05) with functional oil (FctO) compared with olive oil (OL) consumption (?0.67 ± 0.26 kg and ?0.02 ± 0.19 kg, respectively). There was a trend toward greater loss of whole‐body subcutaneous AT volume (p = 0.087) with FctO compared with OL consumption. Average energy expenditure was 0.04 ± 0.02 kcal/min greater (p < 0.05) on day 2 and 0.03 ± 0.02 kcal/min (not significant) on day 28 with FctO compared with OL consumption. Similarly, average fat oxidation was greater (p = 0.052) with FctO compared with OL intake on day 2 but not day 28. Discussion: Consumption of a diet rich in MCTs results in greater loss of AT compared with LCTs, perhaps due to increased energy expenditure and fat oxidation observed with MCT intake. Thus, MCTs may be considered as agents that aid in the prevention of obesity or potentially stimulate weight loss.     

Predictors of Long‐term Weight Maintenance

Objective: The purpose of this study was to evaluate available variables of a long‐term weight maintenance study to investigate possible factors predisposing to weight regain after a period of weight loss. Research Methods and Procedures: The Maastricht Weight Maintenance Study is an ongoing longitudinal study of healthy men and women (29 men and 62 women; 18 to 65 years of age; BMI = 30.2 ± 3.1 kg/m²). A variety of parameters were measured before and after a very‐low‐energy diet and after a follow‐up of at least 2 years. Results: Mean weight loss was 7.9 ± 3.6 kg, and percent weight regain was 113.8 ± 98.1%. Percent BMI regain was negatively associated with an increase in dietary restraint (r = ?0.47, p < 0.05). Percent weight regain was negatively correlated with baseline resting metabolic rate (r = ?0.38, p = 0.01) and baseline fat mass (r = ?0.24, p = 0.05) and positively correlated with the magnitude of change in body weight (BW) expressed as maximum amplitude of BW (r = 0.21, p < 0.05). In addition, amplitude of BW was positively correlated with the frequency of dieting (r = 0.57, p < 0.01). Discussion: The best predictors for weight maintenance after weight loss were an increase in dietary restraint during weight loss, a high baseline resting metabolic rate, a relatively high baseline fat mass favoring a fat‐free mass–sparing effect during weight loss, a rather stable BW, and a low frequency of dieting. Therefore, BW maintenance after BW loss seems to be a multifactorial issue, including mechanisms that regulate an individuals’ energy expenditure, body composition, and eating behavior in such a way that energy homeostasis is maintained.     

High-fat hypocaloric diet modifies carbohydrate utilization of obese rats during weight loss

The effects of fat content in the hypocaloric diet on whole body glucose oxidation and adipocyte glucose transport were investigated in two animal-feeding experiments. Diet-induced obese rats were food restricted to 75% of their previous energy intakes with either a high (45% by calorie) or a low (12% by calorie) corn oil diet for 9 wk (experiment 1) or 10 days (experiment 2). The losses of body weight (P < 0.05) and adipose depot weight (P < 0.05) were less in the 45% compared with the 12% fat group. During the dynamic phase of weight loss (day 10 of food restriction), plasma glucose and insulin concentrations were higher (P < 0.05) in the 45% than those in the 12% fat group. Whole body carbohydrate oxidation rate in response to an oral load of glucose was increased (P < 0.001) by food restriction in both dietary groups; however, carbohydrate oxidation rates were lower (P < 0.01) in the 45% than in the 12% fat-fed rats during the weight loss period. Adipocyte glucose transport was greater (P < 0.02) in the 45% than in the 12% fat group in an intra-abdominal adipose depot but not in subcutaneous fat. These data suggest that dietary fat content modifies whole body glucose oxidation and intra-abdominal adipocyte glucose uptake during weight loss.