Dietary fat and weight gain among women in the Nurses' Health Study

Objective: To assess the association of dietary fat and weight gain among adult women and to investigate whether offspring of overweight parents have a greater predisposition to weight gain due to intake of dietary fat. Research Methods and Procedures: This was an 8‐year follow‐up of 41,518 women in the Nurses’ Health Study (NHS), a population‐based, prospective cohort. The women were 41 to 68 years of age, free of cardiovascular disease, cancer, and diabetes in 1986 when “baseline” weight and diet were assessed. Eight years later (1994), changes in weight and dietary intake were assessed. Linear regression models were used to relate change in weight to fat intake and change in fat intake, using the percentage of energy from carbohydrate as the comparison, adjusted for age, BMI in 1986, leisure time physical activity, time spent sitting, percent of calories from protein, and change in percentage of calories from protein. Results: Overall, there was a weak positive association between total fat intake (β = 0.11) and weight gain. Increases in monosaturated and polyunsaturated fat were not associated with weight gain, but increases in animal fat, saturated fat, and trans fat had a positive association with weight change. There was not strong evidence of effect modification by parental weight status (p = 0.7 to 0.8 for percentage of calories from total fat, animal fat, and vegetable fat); however, the associations were stronger among the overweight compared with leaner women (p < 0.05 for percentage of calories from each type of fat). Among overweight women, for every one percentage increase in percentage of calories from trans fat, women gained an additional 2.3 lb (95% confidence interval, 1.80 to 2.86). Conclusion: Our results show that, overall, percent of calories from fat has only a weak positive association with weight gain; however, percentage of calories from animal, saturated, and trans fat has stronger associations. There was no clear evidence that the diet‐weight gain association was stronger among offspring of overweight parents, but dietary fat was associated with greater weight gain among overweight women.     

Dietary supplementation with Agaricus blazei murill extract prevents diet‐induced obesity and insulin resistance in rats

Objective:

Dietary supplement may potentially help to fight obesity and other metabolic disorders such as insulin‐resistance and low‐grade inflammation. The present study aimed to test whether supplementation with Agaricus blazei murill (ABM) extract could have an effect on diet‐induced obesity in rats.

Design and Methods:

Wistar rats were fed with control diet (CD) or high‐fat diet (HF) and either with or without supplemented ABM for 20 weeks.

Results:

HF diet‐induced body weight gain and increased fat mass compared to CD. In addition HF‐fed rats developed hyperleptinemia and insulinemia as well as insulin resistance and glucose intolerance. In HF‐fed rats, visceral adipose tissue also expressed biomarkers of inflammation. ABM supplementation in HF rats had a protective effect against body weight gain and all study related disorders. This was not due to decreased food intake which remained significantly higher in HF rats whether supplemented with ABM or not compared to control. There was also no change in gut microbiota composition in HF supplemented with ABM. Interestingly, ABM supplementation induced an increase in both energy expenditure and locomotor activity which could partially explain its protective effect against diet‐induced obesity. In addition a decrease in pancreatic lipase activity is also observed in jejunum of ABM‐treated rats suggesting a decrease in lipid absorption.

Conclusions:

Taken together these data highlight a role for ABM to prevent body weight gain and related disorders in peripheral targets independently of effect in food intake in central nervous system.     

Intake of fruits and vegetables in relation to 10-year weight gain among Spanish adults

Objective: Despite the alarming increase in the prevalence of obesity, epidemiologic studies that prospectively examine the fruit and vegetable consumption and other lifestyle factors in relation to weight gain (WG) are still insufficient. We explored the associations between fruit and vegetable intake and WG over a 10‐year period in an adult Mediterranean population. Methods and Procedures: We performed a 10‐year follow‐up study with healthy participants (n = 206) aged 15–80 years at baseline in 1994, who participated in a nutrition survey in Valencia, Spain. Data on diet, lifestyle factors, and body weight were obtained in 1994 and 2004 using a food frequency questionnaire (FFQ) and direct measurements. Results: The average WG over the study period was 3.41 (s.d. 6.9) kg. In multivariate analyses, participants in the third quartile of fruit intake at baseline in 1994 had lower risk of WG ≥ 3.41 kg compared to those in the lowest quartile (oddsratio (OR) = 0.31, 95% confidence interval (CI), 0.11–0.85; P trend = 0.044). Regarding vegetable intake, the risk of WG was lowest in participants of the fourth quartile (>333 g/day), which had an 84% reduced risk of gaining 3.41 kg weight (OR = 0.18, 95% CI, 0.05–0.66; P trend = 0.017). When the intake of fruits and vegetables was combined, the risk of WG decreased across quartiles, with the lowest risk among those in the fourth quartile (OR = 0.22, 95% CI, 0.06–0.81; P trend = 0.022). Further adjustment for an increased intake of fruits and vegetables over the past 10 years reported by participants in 2004 did not appreciably alter the observed ORs. Discussion: Dietary patterns associated with a high intake of fruits and vegetables in Mediterranean populations may reduce long‐term risk of subsequent WG and obesity among adults.     

Evidence in Female Rhesus Monkeys (Macaca mulatta) that Nighttime Caloric Intake is not Associated with Weight Gain

Objective: To evaluate the hypothesis that nighttime consumption of calories leads to an increased propensity to gain weight. Research Methods and Procedures: Sixteen female rhesus monkeys (Macaca mulatta) were ovariectomized and placed on a high‐fat diet to promote weight gain, and we examined whether monkeys that ate a high percentage of calories at night were more likely to gain weight than monkeys that ate the majority of calories during the day. Results: Within 6 weeks post‐ovariectomy, calorie intake and body weight increased significantly (129 ± 14%, p = 0.04; 103 ± 0.91%, p = 0.02, respectively). Subsequent placement on high‐fat diet led to further significant increases in calorie intake and body weight (368 ± 56%, p = 0.001; 113 ± 4.0%, p = 0.03, respectively). However, there was no correlation between the increase in calorie intake and weight gain (p = 0.34). Considerable individual variation existed in the percentage of calories consumed at night (6% to 64% total daily caloric intake). However, the percentage of calorie intake occurring at night was not correlated with body weight (r = 0.04; p = 0.87) or weight gain (r = 0.07; p = 0.79) over the course of the study. Additionally, monkeys that showed the greatest nighttime calorie intake did not gain more weight (p = 0.94) than monkeys that showed the least nighttime calorie intake. Discussion: These results show that eating at night is not associated with an increased propensity to gain weight, suggesting that individuals trying to lose weight should not rely on decreasing evening calorie intake as a primary strategy for promoting weight loss.     

Intake compensates for resting metabolic rate variation in female C57BL/6J mice fed high-fat diets

Objective: The literature is divided over whether variation in resting metabolic rate (RMR) is related to subsequent obesity. We set out to see whether the effect of RMR on weight gain in mice could be revealed with high‐fat feeding. Research Methods and Procedures: Female C57BL/6J mice received a low‐ (10 kcal%fat n = 47), medium‐ (45 kcal%fat n = 50), or high‐fat diet (60 kcal%fat n = 50) for 12 weeks. Pre‐treatment RMR was measured by indirect calorimetry. Body composition was estimated using DXA before and after treatment. Results: Mice on the high‐fat diet gained 39% of body mass, whereas control animals gained 3.5%. There was no interaction between RMR and dietary type on weight gain, and there was no association between weight gain and RMR for any of the treatments. RMR accounted for 2.4% of the variation in pre‐treatment food intake corrected for initial body mass; however, the gradient of this relationship indicated that variations in RMR were, on average, compensated for by adjustments in food intake. Discussion: Individual variations in RMR did not predispose mice to weight gain independent of the dietary treatment. Deviations from the relationship between RMR and food intake were not associated with weight gain. This suggests that variations in energy expenditure, caused by RMR and physical activity, are closely linked to dietary intake, and, therefore, well compensated. Individual variations in the strength of this association may underpin individual variability in the responses to diet.     

Nut consumption and weight gain in a Mediterranean cohort: The SUN study

Objective: To assess the association, in a Mediterranean population, between nut consumption and risk of weight gain (at least 5 kg) or the risk of becoming overweight/obese. Research Methods and Procedures: The Seguimiento Universidad de Navarra project is a prospective cohort of 8865 adult men and women who completed a follow‐up questionnaire after a median of 28 months. Dietary habits were assessed with a previously validated semiquantitative food‐frequency questionnaire. Results: Nine hundred thirty‐seven participants reported a weight gain of ≥5 kg at follow‐up. After adjusting for age, sex, smoking, leisure time physical activity, and other known risk factors for obesity, participants who ate nuts two or more times per week had a significantly lower risk of weight gain (odds ratio: 0.69; 95% confidence interval: 0.53 to 0.90, p for trend = 0.006) than those who never or almost never ate nuts. Participants with little nut consumption (never/almost never) gained an average of 424 grams (95% confidence interval: 102 to 746) more than frequent nut eaters. Nut consumption was not significantly associated with incident overweight/obesity in the cohort. Discussion: Frequent nut consumption was associated with a reduced risk of weight gain (5 kg or more). These results support the recommendation of nut consumption as an important component of a cardioprotective diet and also allay fears of possible weight gain.     

Comparison of Fat Storage between Fischer 344 and Obesity‐Resistant Lou/C Rats Fed Different Diets**

Objective: We aimed to characterize further the Lou/C (LOU) and Fischer 344 (F344) rat strains for nutritional traits to validate their use as contrasting strains for molecular genetic studies. Research Methods and Procedures: Five batches of LOU and F344 rats were used to measure caloric intake, weight gain, and body composition when fed a chow diet, a self‐selection diet (together with the study of preferences for macronutrients), hypercaloric diets, and a chow diet in a cold environment. Results: Despite a higher caloric intake when fed a chow diet, LOU rats showed a lower weight gain, final body weight, and percentage of fat tissue, together with a higher percentage of carcass weight, than F344 rats. When fed a self‐selection diet, LOU males ingested less protein and more fat than F344 males, and the reverse was observed for females. In this condition, feed efficiency was reduced in LOU but increased in F344 rats compared with the chow diet. Diet‐induced obesity was observed in F344 rats but not in LOU rats fed hypercaloric diets. In a cold environment, both LOU and F344 rats displayed an increased percentage of brown adipose tissue compared with control groups, together with a higher caloric intake. Discussion: The study shows robust nutritional differences between the LOU rat, a lean strain with a low feed efficiency and resistant to diet‐induced obesity, and the contrasting F344 rat strain. It also shows the interest in these strains for studying the genetic components of resistance to obesity.     

Fat Intake Affects Adiposity,Comorbidity Factors,and Energy Metabolism of Sprague‐Dawley Rats

Objective: Childhood obesity is an emerging health problem. This study assesses the effects of three levels of dietary fat (10%, 32%, and 45% measured by kilocalories) on weight gain, body composition, energy metabolism, and comorbidity factors in rats from weaning through maturation. Research Methods and Procedures: The role of dietary fat on the susceptibility to obesity was assessed by feeding diets containing three levels of dietary fat to rats from weaning through 7 months of age. Body composition was analyzed by DXA after 6 and 12 weeks of dietary treatment. Energy metabolism was measured by indirect calorimetry. Results: Energy intake, weight gain, fat mass, and plasma glucose, cholesterol, triglyceride, free fatty acid, leptin, and insulin levels increased dose‐dependently with increased dietary fat. No difference in absolute lean mass among the three groups was observed. Therefore, the differences in weight gain are accounted for primarily by increased fat accretion. Compared with rats that were relatively resistant to obesity when on a 45% fat diet, diet‐induced obesity‐prone rats were in positive energy balance and had an elevated respiratory quotient, indicating a switch in energy substrate use from fat to carbohydrate, which promotes body‐fat accretion. Discussion: Our data support the hypothesis that administration of increasing amount of dietary fat to very young rats enhances susceptibility to diet‐induced obesity and its comorbidities.     

Diet‐Induced Changes in Stearoyl‐CoA Desaturase 1 Expression in Obesity‐Prone and ‐Resistant Mice

Objective: To investigate stearoyl‐coenzyme A desaturase (SCD) 1 expression in obesity‐prone C57BL/6 mice and in obesity‐resistant FVB mice to explore the relationship of SCD1 expression and susceptibility to diet‐induced obesity. Research Methods and Procedures: Nine‐week‐old C57BL/6 and FVB mice were fed either a high‐ or low‐fat diet for 8 weeks. Body weight and body composition were measured before and at weeks 4 and 8 of the study. Energy expenditure was measured at weeks 1 and 5 of the study. Hepatic SCD1 mRNA was measured at 72 hours and at the end of study. Plasma leptin and insulin concentrations were measured at the end of study. Results: When C57BL/6 mice were switched to a calorie‐dense high‐fat diet, animals gained significantly more body weight than those maintained on a low‐calorie density diet primarily due to increased fat mass accretion. Fat mass continued to accrue throughout 8 weeks of study. Increased calorie intake did not account for all weight gain. On the high‐fat diet, C57BL/6 mice decreased their energy expenditure when compared with mice fed a low‐fat diet. In response to 8 weeks of a high‐fat diet, SCD1 gene expression in liver increased >2‐fold. In contrast, feeding a high‐fat diet did not change body weight, energy expenditure, or SCD1 expression in FVB mice. Discussion: Our study showed that a high‐fat hypercaloric diet increased body adiposity first by producing hyperphagia and then by decreasing energy expenditure of mice susceptible to diet‐induced obesity. Consumption of a high‐fat diet in species predisposed to obesity selectively increased SCD1 gene expression in liver.     

Trends and dietary determinants of overweight and obesity in a multiethnic population

Objectives : To describe trends in BMI among different ethnic groups in Hawaii and to explore the relation of nutrient and food intake with excess weight. Research Methods and Procedures : We pooled demographic, anthropometric, and nutritional data derived from a detailed diet history for 159, 683 participants of 18 population‐based epidemiological studies conducted in Hawaii over a 25‐year period. The age‐adjusted prevalence of excess weight (BMI ≥ 25 kg/m²) was estimated for 5‐year intervals. To explore dietary determinants of excess weight, we computed odds ratios using logistic regression. Results : During the study period, the prevalence of excess weight increased considerably among all ethnic groups. Native Hawaiians had the highest and Asian Americans had the lowest prevalence of excess weight at all times. Although the percentage of calories consumed from carbohydrates increased, the percentage of calories from fat decreased over time. On an individual level, fat and protein consumption predicted a higher BMI, and dietary fiber intake predicted a lower BMI. Similarly, a higher consumption of meat, poultry, and fish was related to excess weight, whereas fruit and vegetable intake were inversely associated with excess weight. After stratification by ethnicity, the associations were not materially altered among women, but carbohydrates seemed to have a stronger association with excess weight among Native Hawaiian and Japanese men than among white men. Discussion : In this large ethnically diverse population, plant‐based foods and dietary fiber emerged as a potential protective factor against excess weight regardless of ethnicity.     

Oligofructose Promotes Satiety in Rats Fed a High‐Fat Diet: Involvement of Glucagon‐Like Peptide‐1

Objective: To analyze the putative interest of oligofructose (OFS) in the modulation of food intake after high‐fat diet in rats and to question the relevance of the expression and secretion of intestinal peptides in that context. Research Methods and Procedures: Male Wistar rats were pretreated with standard diet or OFS‐enriched (10%) standard diet for 35 days followed by 15 days of high‐fat diet enriched or not with OFS (10%) treatment. Body weight, food intake, triglycerides, and plasma ghrelin levels were monitored during the treatment. On day 50, rats were food‐deprived 8 hours and anesthetized for blood and intestinal tissue sampling for further proglucagon mRNA, glucagon‐like peptide (GLP)‐1, and GLP‐2 quantification. Results: The addition of OFS in the diet protects against the promotion of energy intake, body weight gain, fat mass development, and serum triglyceride accumulation induced by a high‐fat diet. OFS fermentation leads to an increase in proglucagon mRNA in the cecum and the colon and in GLP‐1 and GLP‐2 contents in the proximal colon, with consequences on the portal concentration of GLP‐1 (increase). A lower ghrelin level is observed only when OFS is added to the standard diet of rats. Discussion: In rats exposed to high‐fat diet, OFS is, thus, able to modulate endogenous production of gut peptides involved in appetite and body weight regulation. Because several approaches are currently used to treat type 2 diabetes and obesity with limited effectiveness, dietary fibers such as OFS, which promote the endogenous production of gut peptides like GLP‐1, could be proposed as interesting nutrients to consider in the management of fat intake and associated metabolic disorders.     

Normal Distribution of Body Weight Gain in Male Sprague‐Dawley Rats Fed a High‐Energy Diet

Objective: To investigate the effect of a high‐energy (HE) diet on caloric intake, body weight, and related parameters in outbred male Sprague‐Dawley (SD) rats. Research Methods and Procedures: Twenty‐eight SD rats were fed either chow (C) for 19 weeks or HE diet for 14 weeks and then C for 5 weeks. Blood hormones and metabolites were assayed, and expression of uncoupling protein‐1 and hypothalamic energy‐balance‐related genes were determined by Northern blotting and in situ hybridization, respectively. Results: HE rats gained body weight more rapidly than C animals with a range of weight gains, but there was no evidence that weight gain was bimodally distributed. Caloric intake was transiently elevated after introduction of the HE diet. Transfer of HE rats back to C resulted in a drop in caloric intake, but a stable body weight. In terminal analysis, two of four dissected adipose tissue depots were heavier in rats that had previously been fed HE diet. Blood leptin, insulin, glucose, and nonesterified fatty acids were not different between the groups. Uncoupling protein‐1 mRNA was elevated in interscapular brown adipose tissue from HE rats. There was a trend for agouti‐related peptide mRNA in the hypothalamic arcuate nucleus to be higher in HE rats. Discussion: Contrary to other studies of the SD rat on HE diet, body weight and other measured parameters were normally distributed. There was no segregation into two distinct populations on the basis of susceptibility to diet‐induced obesity. This characteristic may be dependent on the breeding colony from which animals were sourced.     

Sedentary behavior, recreational physical activity, and 7-year weight gain among postmenopausal U.S. women

Objective: To assess the relationship among recreational physical activity (PA), non‐occupational sedentary behavior, and 7‐year weight gain among postmenopausal U.S. women 40 to 69 years old. Research Methods and Procedures: In 1992 and 1999, 18,583 healthy female participants from the Cancer Prevention Study II Nutrition Cohort completed questionnaires on anthropometric characteristics and lifestyle factors. The associations between recreational PA [in metabolic equivalent (MET) hours per week] and non‐occupational sedentary behavior (in hours per day) at baseline and risk for 7‐year weight gain (5 to 9 or ≥10 vs. ±4 pounds) were assessed using multivariate logistic regression analysis. Results: Neither PA nor sedentary behavior was associated with a 5‐ to 9‐pound weight gain. Among women who were not overweight at baseline (BMI <25.0), the odds of ≥10‐pound weight gain were 12% lower (odds ratio, 0.88; 95% confidence interval, 0.77 to 0.99) for those in the highest category of recreational PA (≥18 MET h/wk) compared with >0 to <4 MET h/wk; odds were 47% higher (odds ratio, 1.47; 95% confidence interval, 1.21 to 1.79) for non‐overweight women who reported ≥6 h/d of non‐occupational sedentary behavior compared with <3 h/d. Neither PA nor sedentary behavior were associated with risk of ≥10‐pound weight gain weight among women who were overweight at baseline (BMI ≥25.0). Discussion: Both recreational PA and non‐occupational sedentary behavior independently predicted risk of ≥10‐pound weight gain among postmenopausal women who were not overweight at baseline. Public health messages to prevent weight gain among normal‐weight postmenopausal women may need to focus on decreasing time spent in sedentary behaviors and increasing the amount of time spent on PA.     

Zinc‐Induced Hyperleptinemia Relates to the Amelioration of Sucrose‐Induced Obesity with Zinc Repletion

Objective: Dietary zinc repletion can ameliorate sucrose‐induced obesity. A positive correlation between zinc and leptin has been recently noted, and both are known as important mediators in appetite control. In this study, we examined whether the reported amelioration of sucrose‐induced obesity by zinc repletion was consequent on the changes in circulating leptin levels. Research Methods and Procedures: Mice with obesity that was induced by giving a 32% sucrose solution in addition to a semipurified diet were divided into two groups based on whether they had 20 mg/liter zinc supplementation in their drinking water. Results: As expected, the mice with sucrose‐induced obesity had hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hyperleptinemia, and hypozincemia when compared with the mice given the diet alone. Body weight gain, body fat content, and food and sucrose intake tended to decrease but not with statistical significance in sucrose‐fed obese mice with zinc supplementation. Nevertheless, some serum variables (glucose, insulin, triglycerides, and zinc) in sucrose‐fed obese mice with zinc treatment were approximate to those values of the mice given the diet alone. Moreover, sucrose‐fed obese mice with zinc supplementation had the highest serum values of leptin. Discussion: This study indicates that the amelioration of sucrose‐induced obesity by zinc repletion may be partly attributable to the hyperleptinemia induced by the mineral.     

S 23521 Decreases Food Intake and Body Weight Gain in Diet‐Induced Obese Rats

Objective: To investigate the effect of S 23521, a new glucagon‐like peptide‐1‐(7‐36) amide analogue, on food intake and body weight gain in obese rats, as well as on gene expression of several proteins involved in energy homeostasis. Research Methods and Procedures: Lean and diet‐induced obese rats were treated with either S 23521 or vehicle. S 23521 was given either intraperitoneally (10 or 100 μg/kg) or subcutaneously (100 μg/kg) for 14 and 20 days, respectively. Because the low‐dose treatment did not affect food intake and body weight, the subcutaneous treatment at high dose was selected to test the effect on selected end‐points. Results: Treated obese rats significantly decreased their cumulative energy intake in relation to vehicle‐treated counterparts (3401 ± 65 vs. 3898 ± 72 kcal/kg per 20 days; p < 0.05). Moreover, their body weight gain was reduced by 110%, adiposity was reduced by 20%, and plasma triglyceride levels were reduced by 38%. The treatment also improved glucose tolerance and insulin sensitivity of obese rats. Regarding gene expression, no changes in uncoupling protein‐1, uncoupling protein‐3, leptin, resistin, and peroxisome proliferator‐activated receptor (PPAR)‐γ were observed. Discussion: S 23521 is an effective glucagon‐like peptide‐1‐(7‐36) amide analogue, which induced a decrease in energy intake, body weight, and adiposity in a rat model of diet‐induced obesity. In addition, the treatment also improved glucose tolerance and insulin sensitivity of obese rats. These results strongly support S 23521 as a putative molecule for the treatment of obesity.     

Maintenance of weight loss in overweight middle-aged women through the Internet

Objective: The purpose of this study was to compare weight regain in a group of perimenopausal women (48.0 ± 4.4 years old), randomized to a 12‐month weight maintenance Internet intervention or to self‐directed weight maintenance after a 4‐month weight loss treatment. Methods and Procedures: After a 4‐month behavioral weight loss program, 135 women were randomized to either Internet or self‐directed groups. The Internet group (n = 66) used a website to gain information and complete logs concerning their weight, diet, and exercise progress over a 12‐month follow‐up. The 69 self‐directed women had no contact with study staff. All women were measured for weight and body composition, and diet intake, and were interviewed using the 7‐day physical activity questionnaires at baseline, 4 months, and 16 months. Results: At the end of the 12‐month follow‐up, the Internet and self‐directed groups had regained on average 0.4 ± 5.0 kg and 0.6 ± 4.0 kg, respectively (P = 0.5). In within‐group analyses, Internet diet‐log entries were correlated with follow‐up weight change (r = ?0.29; P < 0.05) and moderately with change in exercise energy expenditure (EEE; r = 0.44; P < 0.01). Follow‐up weight change was not correlated with change in dietary intake. Discussion: While significant weight loss was maintained over follow‐up by both groups of women, Internet use did not surpass self‐direction in helping to sustain weight loss. Among Internet users, Internet use was related to weight change and EEE.     

Meal Pattern Analysis of Diet‐Induced Obesity in Susceptible and Resistant Rats

Objective: To characterize the meal patterns of free feeding Sprague‐Dawley rats that become obese or resist obesity when chronically fed a high‐fat diet. Research Methods and Procedures: Male Sprague‐Dawley rats (N = 120) were weaned onto a high‐fat diet, and body weight was monitored for 19 weeks. Rats from the upper [diet‐induced obese (DIO)] and lower [diet‐resistant (DR)] deciles for body‐weight gain were selected for study. A cohort of chow‐fed (CF) rats weight‐matched to the DR group was also studied. Food intake was continuously monitored for 7 consecutive days using a BioDAQ food intake monitoring system. Results: DIO rats were obese, hyperphagic, hyperleptinemic, hyperinsulinemic, hyperglycemic, and hypertriglyceridemic relative to the DR and CF rats. The hyperphagia of DIOs was caused by an increase in meal size, not number. CF rats ate more calories than DR rats; however, this was because of an increase in meal number, not size. When expressed as a function of lean mass, CF and DR rats consumed the same amount of calories. The intermeal intervals of DIO and DR rats were similar; both were longer than CF rats. The nocturnal satiety ratio of DIO rats was significantly lower than DR and CF rats. The proportion of calories eaten during the nocturnal period did not differ among groups. Discussion: The hyperphagia of a Sprague‐Dawley rat model of chronic diet‐induced obesity is caused by an increase in meal size, not number. These results are an important step toward understanding the mechanisms underlying differences in feeding behavior of DIO and DR rats.