Effect of treadmill exercise on food intake and body weight in lean and obese rats

Body weight and food intake of lean and obese, male and female Osborne-Mendel rats following treadmill exercise were compared. Rats were assigned, separately by sex, to one of three diet groups; Group 1 was fed a low fat (10%) diet throughout the study, Group 2 was fed a high fat (55%) diet for 16 weeks and then switched to the low fat diet 1 week prior to exercise, and Group 3 was fed the high fat diet throughout the study. To control for differences in work output between the leanest and heaviest animals, exercise intensity was adjusted across groups such that all exercised rats had equivalent energy expenditure. After a 3 day training period, the exercise was successively increased over 8 days until a work output of 374.9J was reached. Relative to their respective controls, obese exercised males showed a reduction in body weight but no change in food intake. In contrast, exercised females showed no change in body weight or food intake, regardless of dietary condition.     

Effects of diet and exercise training on thermogenesis in adult female rats

The effects of a cafeteria diet on body weight gain, food intake, resting metabolic rate (RMR) and the thermic effect of food (TEF) were compared in female Charles River albino rats that were either sedentary or exercise-trained. The food intakes of the exercise-trained rats on the cafeteria diet were increased to the same degree as those of the sedentary rats, however, they gained less body weight and body fat than sedentary controls. The exercise training increased RMR independent of diet, but differentially increased TEF in rats given the cafeteria diet. Conversely, sedentary rats on the cafeteria diet had significantly lower RMR, but their TEF were not different from control animals on lab chow. Thus, in addition to the direct cost of the exercise, training increased thermogenesis (RMR and TEF) which also helped prevent the dietary obesity which normally occurs with cafeteria diets.     

Effect of dietary macronutrients on food intake, body weight, and tail width in the marsupial S. crassicaudata

The role of dietary fat, as opposed to total energy intake, in the etiology of obesity is controversial. The aim of this study was to determine the effect of macronutrient content, specifically changes in dietary fat on body weight, fat stores, and food intake in S. crassicaudata, a marsupial that stores about 25% of total body fat in its tail. Female animals were divided into three groups (n = 7-9) matched for food intake per gram of body weight. Each group of animals was fed, ad lib an isocaloric diet (1.01 kcal/g), which contained either 10, 20, or 40% of calories from fat. Body weight, food intake, and tail width (an index of body fat stores) were measured daily. Over 21 days, cumulative energy intake was less (p = 0.026) in the 40% fat group compared to the 10% fat group. Despite the differences in food intake, body weight in each group remained stable throughout the study, so that at day 21 there were no differences in the body weights between the three groups. In contrast, tail width increased in the animals who received the 40% fat diet compared to either the 10% (p = 0.016) or 20% (p = 0.001) fat intake groups, whereas there was no significant change in tail width in either of these two groups. These observations indicate that macronutrient composition has a role, independent of total calories in the regulation of food intake and body fat stores, specifically that dietary fat promotes adiposity, independent of total caloric intake.     

Physiological effects of dieting and bingeing in rats.

Female rats were assigned to dietary conditions as follows for 3.5 months: 1) Low-fat control (LFC); 2) Moderately high-fat control (HFC); 3) Alternation between restricted access to a low-fat diet and ad lib access to a very high fat diet (RA); 4) Unrestricted access to the same diets as RA (URA). Results indicate that: 1) HFC consumed the same energy as LFC, but showed a tendency to become heavier and fatter through greater food efficiency. 2) URA and LFC did not differ in body weight, food intake, body composition or energy efficiency. 3) Intake of the very high fat diet declined over time in the RA. 4) RA ate less total calories, weighed less than all other groups, and showed a tendency for decreased percentage body fat and increased percentage of weight gained due to FFM gained. Results provide no evidence that dieting and bingeing promote obesity or increased preference for dietary fat, and suggest that dietary restriction has greater impact on energy balance and body composition than does alternation of diet composition.     

Pro-opiomelanocortin gene transfer to the nucleus of the solitary track but not arcuate nucleus ameliorates chronic diet-induced obesity

Short-term pharmacological melanocortin activation deters diet-induced obesity (DIO) effectively in rodents. However, whether central pro-opiomelanocortin (POMC) gene transfer targeted to the hypothalamus or hindbrain nucleus of the solitary track (NTS) can combat chronic dietary obesity has not been investigated. Four-weeks-old Sprague–Dawley rats were fed a high fat diet for 5 months, and then injected with either the POMC or control vector into the hypothalamus or NTS, and body weight and food intake recorded for 68 days. Insulin sensitivity, glucose metabolism and adrenal indicators of central sympathetic activation were measured, and voluntary wheel running (WR) assessed. Whereas the NTS POMC-treatment decreased cumulative food consumption and caused a sustained weight reduction over 68 days, the hypothalamic POMC-treatment did not alter cumulative food intake and produced weight loss only in the first 25 days. At death, only the NTS-POMC rats had a significant decrease in fat mass. They also displayed enhanced glucose tolerance, lowered fasting insulin and increased QUICK value, and elevated adrenal indicators of central sympathetic activation. Moreover, the NTS-POMC animals exhibited a near 20% increase in distance ran relative to the respective controls, but the ARC-POMC rats did not. In conclusion, POMC gene transfer to the NTS caused modest anorexia, persistent weight loss, improved insulin sensitivity, and increased propensity for WR in DIO rats. These metabolic improvements may involve stimulation of energy expenditure via centrally regulated sympathetic outflow. The similar POMC treatment in the hypothalamus had minimal long-term physiological or metabolic impact. Thus, melanocortin activation in the brainstem NTS region effectively ameliorates chronic dietary obesity whilst that in the hypothalamus fails to do so.     

Role of gonadal hormones in diet selection and food utilization in female rats

Patterns of dietary self-selection were examined in ovariectomized and sham-operated female rats. Self-selection animals were offered separate dietary sources of protein, carbohydrate, and fat. Control animals were offered ground Purina Rodent Chow. Food intakes, water intakes, and body weights were measured daily for all animals. During a 19-day baseline period, selecting animals chose approximately one third of their daily caloric intake from each of the three diet sources. Following this baseline period, half of the self-selection animals and half of the control animals received bilateral ovariectomies, while the remaining animals in each diet group received sham-operations. Following ovariectomies, both self-selection and control animals significantly increased food intakes and rate of weight gains above baseline values. In contrast, sham-operated animals did not increase food intakes or rate of weight gain following surgery. When weight gain was calculated as a function of caloric intake, ovariectomized animals gained nearly twice as much weight per kilocalorie consumed as sham-operated animals. Ovariectomized animals showed no changes in diet selection after surgery, while sham-operated animals showed a slight decrease in the percentage protein selected. Differences between self-selection patterns in ovariectomized animals and in animals with other forms of experimentally-induced obesity suggest distinct metabolic patterns may underlie various forms of obesity.     

Effects of exercise-training on the thermic effect of food and body fatness of adult women

Resting metabolic rate (RMR), thermic effect of food (TEF), aerobic capacity (VO2max), body fat, and food intake were measured in 10 healthy women before and after a 10 week graded exercise program of jogging. Pretraining TEF was a linear function of VO2max. Following exercise training, the women showed a significant increase (20%) in VO2max and loss (10.4%) of body fat; body weight did not change. Fat loss was directly related to changes in VO2max and RMR. The women showed a wide variation of changes in RMR (-21 to +2%) and TEF (-32 to +66%) from their pretraining levels. The changes in RMR and TEF were significantly positively correlated with improvements in VO2max. Analyses using multiple regression techniques, indicated that the changes in RMR and TEF accounted for 96.2% of the total variation in the changes of VO2max. Analyses of food intake indicated that diet composition (but not caloric intake) was highly related to the changes in VO2max, RMR, TEF and body fatness. Present results support further our hypothesis, that VO2max is an important physiological index of dietary thermogenesis and fat loss of individuals of normal body weight and fatness. Possible nutritional and physiological factors that may explain the wide variation in RMR and TEF of the women are discussed.     

Effects of dietary caloric density on feeding behavior in Mongolian gerbils (Meriones unguiculatus)

Total daily energy intake, water intake, body weight, and meal patterns were studied in Mongolian gerbils as a function of dietary caloric density. On diets ranging in caloric density from 2.25 kcal/g to 6.09 kcal/g, gerbils consumed an average of 40 kcal per 100 g of body weight per day. In comparison to gerbils fed ground Purina Laboratory Chow (4.2 kcal/g), gerbils presented with diets diluted with nonutritive cellulose increased food intake in proportion to the percentage of cellulose added. Gerbils given diets in which the caloric density was increased by the addition of fat, decreased food intake as a direct function of the added fat. Water intake was increased on the calorically diluted diets, and decreased on the concentrated diets. Body weight did not vary as a function of dietary conditions. On a standard pelleted diet (Noyes), gerbils ate approximately 18 meals a day. Average meal size was 0.4 g. When presented with calorically diluted pellets, gerbils maintained daily energy intake by increasing both meal frequency and meal size. There were no differences in food intake, meal frequency or meal size between the light and dark portions of the 24-hr cycle.     

Effect of hydroxycitrate on food intake and body weight regain after a period of restrictive feeding in male rats

We examined whether dietary supplementation of hydroxycitrate (HCA), a competitive inhibitor of the extramitochondrial enzyme ATP-citrate-lyase, which inhibits lipogenesis, reduces food intake and body weight regain in rats after 10-15% weight loss. In four experiments, 24 male rats were fed restrictively (10 g/day) for 10 days and then given ad lib access to one of four different diets (HI-Suc=high sucrose; HI-Glu=high glucose; Chow=grounded standard rat chow; HI-Glu+Fat=high glucose+fat) varying in the content of fat and low molecular carbohydrates for the following 10 days. For half of the rats (n=12), the ad lib diet was supplemented with 3% (w/w) HCA. HCA reduced body weight regain with all diets except Chow. HCA also reduced food intake temporarily with three of the four tested diets. The suppressive effect of HCA on food intake was particularly strong with the HI-Glu+Fat diet (fat=24% of energy). With Diet HI-Glu and HI-Glu+Fat HCA reduced the feed conversion efficiency (cumulative body weight regain (g)/cumulative food intake (MJ)) during the 10 ad lib days, suggesting that it also increased energy expenditure. This effect seemed to be positively related to the glucose content of the diet. All in all, HCA reduced body weight regain after substantial body weight loss, and the effects are presumably linked to its inhibiting effect on lipogenesis, but the exact mechanism still has to be determined.     

Dietary hyperphagia in rats: role of fat, carbohydrate, and energy content

Dietary energy, fat and carbohydrate content were varied to determine the nutritional factors responsible for hyperphagia induced by feeding rats high-fat diets. In the first experiment, rats were fed isoenergetic high-fat or high-carbohydrate diets for 2 weeks. Weight gain and energy intake were lower in rats given the high-fat diet. When some of the rats were switched to a diet that was high in fat, carbohydrate and energy, gram food intake was initially unchanged, resulting in a substantial increase in energy intake and weight gain. Energy intake gradually declined over the 4 weeks following the switch to the high-energy diet. In the second experiment, rats were fed high-fat diets that were either high or low in carbohydrate content and either high or low in energy content (kcal/g). Rats fed a high-fat diet that was high in energy and carbohydrate ate the most energy and gained the most body weight and carcass fat. In the third experiment, rats were fed high-carbohydrate diets varying in fat and cellulose content. Energy intake and body weight gain varied directly as a function of caloric density regardless of the fat or cellulose content of the diets. It is concluded that hyperphagia induced by feeding high-fat diets is not due to the high dietary fat content alone. Rather, high levels of fat, carbohydrate, and energy interact to produce overeating and obesity in rats fed high-fat diets.     

Sex differences in the effects of voluntary activity on sucrose-induced obesity

Sedentary, adult rats of both sexes fed Purina chow and a 32% sucrose solution overate, gained excess weight and had higher Lee Indexes of obesity than control animals fed only Purina chow. The magnitude of these effects was similar in the males and females. Animals of both sexes fed the sucrose diet showed a slower rate of weight loss during food deprivation than the chow controls. Access to an activity wheel led to a reduction in caloric intake and the elimination of obesity in male rats. In the chow fed male rats activity led to a smaller, transient suppression in caloric intake and a slightly lower level of body weight than the sedentary chow controls. Access to activity did not affect body weight in the female rats in either dietary condition. Rather, both active groups of female rats appeared to compensate for the energy cost of voluntary activity by a small increase in food consumption. Long-term exposure to activity was associated with more rapid weight loss during food deprivation in both males and females. These data reveal that high levels of activity and obesity can co-exist when normal female rats are fed a palatable diet but that activity eliminates this form of obesity in the male rat.     

Aversion of the cat to dietary medium-chain triglycerides and caprylic acid

Young, specific-pathogen-free cats were fed purified diets containing different sources of fat. Food intake was depressed and cats lost weight when the diet contained either hydrogenated coconut oil (HCO) or medium-chain triglycerides (MCT). With an MCT preparation enriched in 8:0 (MCT8), cats would not eat after first tasting the diet. When cats were offered a choice of two high-fat diets, they chose the basal diet over a diet containing 30% HCO, by a ratio of 4.5:1. Low levels of MCT8 (5% or 10% by weight) were also rejected, whereas cats did not reject 5% or 15% MCT12. Caprylic acid, at 0.1-1.0% of the diet, was rejected. In other studies, food intake and body weight decreased when HCO was added to a fat-free diet. Cats fed 25% or 35% HCO lost weight. When 5% safflower seed oil was added to the HCO diets, body weights and food intake improved, but were still less than optimal. These studies indicate that the food intake depression in cats fed dietary HCO and MCT is primarily a result of impalatability, and that the fatty acid moiety may be responsible for the aversion.     

Protein selection, food intake, and body composition in response to the amount of dietary protein

Though not universally observed, moderately low-protein diets have been found to increase caloric intake and body fat. It appears that animals overeat in calories in order to obtain more dietary protein. For animals to control protein intake, they must be able to distinguish between two isocaloric diets containing different percentages of protein and make the appropriate dietary selection on the basis of their previous history of protein intake. Experiment 1 examined the 24-h diet selection (5 vs. 35% casein) of Sprague-Dawley rats that had been previously fed diets containing various percentages of dietary protein (5, 10, 20, 35, or 60% casein). Animals fed 5, 10, or 20% dietary protein showed a preference for the higher protein selection diet. In contrast, no significant diet preference was found in animals pre-fed the two higher levels of dietary protein (35 or 60% casein). In this study, daily food intake and body fat of rats fed the low-protein diets (5 and 10% casein) were similar to rats fed the 20% casein diet. Experiment 2 examined the effects of the level of methionine supplementation on rats fed 10% casein. In this study, food intake and body fat were increased by approximately 20% in rats fed 10% casein diets, regardless of the level of methionine supplementation (0.3 vs. 0.15%). Together, the results suggest that the presence of low-protein-induced hyperphagia helps maintain body protein levels in the face of moderately low dietary protein and promotes an increase in the amount of body fat and energy.     

Exercise and the development and persistence of dietary obesity in male and female rats

Adult male and female hooded rats were housed in sedentary conditions or were given free access to a running wheel. Exercising and sedentary rats received either a palatable, mixed, high energy diet with chow (experimental group) or only chow (control group). Exercise reduced the weight gain of the males but not of the females. All experimental groups preferentially selected the palatable foods. Both exercising and sedentary females and the sedentary males became obese compared to their controls, but the exercising males did not. The mixed diet was withdrawn after 10 weeks: thereafter the male and female sedentary experimental groups maintained the elevated body weight. The exercising experimental females showed significant weight loss. Analysis of x-ray photographs indicated that elevated body weight in the experimental rats probably reflected increased deposition of fat and not skeletal growth. The results show that the effect of exercise on the development of dietary obesity is different in males and females, and that sedentary male and female rats can both show persistent dietary obesity after withdrawal of the palatable foods.     

Calcium deficiency cannot induce obesity in rats

If intake of a required nutrient--here calcium--affects body weight, the effect must be mediated by a change in the body weight set-point. Thus, the controversial 'anti-obesity' influence of high calcium intake should decrease the body weight set-point. Diets differing in calcium content were assigned to three groups of rats. The effects of the diets on body weight, BMI, fat content, plasma calcium, body weight set-point, food intake, and preference for various calcium solutions were measured after 6 weeks of calcium deprivation or supplementation, and again after a further 6 weeks of recovery on a regular diet. After 6 weeks, the low-calcium diet had induced calcium deficiency but had failed to raise the body weight set-point. Nor had it produced obesity or fat accumulation. After 6 weeks of recovery, body weight and fat content were no higher in calcium-deprived rats than in the control or supplemented rats. In this experiment, low-calcium intake failed to cause obesity and did not raise the body weight set-point. The results indicate that calcium intake probably does not affect body weight.     

Spontaneous motor activity during the development and maintenance of diet-induced obesity in the rat.

More than 80% of most daily spontaneous activities (assessed in an Omnitech activity monitor) occurred during the last hour of light and 12 h of the dark phase in 8 chow-fed male Sprague-Dawley rats. Thirty additional rats were, therefore, monitored over this 13-h period to assess the relationship of activity to the development and maintenance of diet-induced obesity (DIO) on a diet high in energy, fat and sucrose (CM diet). Nine of 20 rats became obese after 3 months on the CM diet, with 71% greater weight gain than 10 chow-fed controls. Eleven of 20 rats were diet resistant (DR), gaining the same amount of weight as chow-fed rats. Neither initial activity levels nor initial body weights on chow (Period I) differed significantly across retrospectively identified groups. After 3 months on CM diet or chow (Period II), as well as after an additional 3 months after CM diet-fed rats returned to chow (Period III), there were significant inverse correlations (r = -.606 to -.370) between body weight at the time of testing and various measures of movement in the horizontal plane. There was no relationship to dietary content nor consistent correlations of body weight or diet group to vertical movements, an indirect measure of ingestive behavior. Patterns of time spent in the vertical position were significantly different for DIO vs. DR rats in Period III, however. Thus, differences in food intake and metabolic efficiency, rather than differences in nocturnal activity, are probably responsible for the greater weight gain in DIO-prone rats placed on CM diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of early dietary experience on energy regulation in rats

The environmental mechanisms that have contributed to the rapid increases in overweight and obesity in the US over the past 25-30 years have yet to be fully specified. One hypothesis that has been forwarded is that increased consumption of calories in liquid form may be a contributing factor, since some studies support the idea that caloric compensation is less adequate for liquid calories compared to calories delivered in more solid form. Work from our laboratory using rats has examined the role that differences in diet viscosity may play in altering energy intake and body weight regulation. This work has suggested that when offered diets matched on caloric density, macronutrient and micronutrient composition, and differing only in viscosity, adult rats fail to compensate for calories delivered in low-viscosity form in short-term intake tests. Further, long-term consumption of low-viscosity diets leads to enhanced weight gain in adult rats. In the present studies, we examined whether short- or long-term exposure to varying relationships between viscosity and calories led to altered food intake or body weight regulation in juvenile rats. The results demonstrated that animals given either short- or long-term experience with direct relationships between viscosity and calories (high viscosity, high calorie meals and low viscosity, low calorie meals) did not differ in food intake or body weight gain compared to animals given short- or long-term experience with indirect relationships between viscosity and calories (high viscosity, low calorie meals and low viscosity, high calorie meals). When juvenile rats were given long-term (9 weeks) exposure to a single, high or low viscosity diet supplement, matched on caloric density and differing only in viscosity, there were no effects on body weight gain. However, analysis of body composition using DEXA demonstrated that animals consuming the low viscosity supplements had significantly greater body fat than animals that consumed either the high viscosity supplement or no dietary supplement at all. These differences in body fat persisted for at least 3 months following the cessation of dietary supplements; during this 3-month period, animals previously exposed to the low viscosity supplement also gained significantly more weight than animals previously exposed to the high viscosity supplement. Taken together, the results suggest that consuming calories in low viscosity form may contribute to poor intake regulation over the short-term and to increased adiposity over the long term. When animals experience these diets as juveniles, these effects may persist into adulthood.     

Physical activity, fat intake and body fat

The body fatness of a subject is a long-term reflection of the energy balance, the more intake exceeds expenditure the more energy is stored as fat. There is not yet a clear answer on the question whether the current obesity epidemic is a consequence of gluttony or sloth. Review studies do not show a reduction of physical activity over the years, and food intake is difficult to measure in daily life conditions. Food intake can only be derived from self-report, where under-reporting of food intake and selective underreporting of fat intake are major issues. Fat intake might be an important factor in the increase of body weight. Many studies suggest the capacity of the body to oxidize dietary fat is a major risk factor for a positive energy balance. Additionally, there is evidence that most of the fat consumed is stored before oxidation. Obesity prone subjects might be characterized by a higher storage of dietary fat. The only way to increase the oxidation of dietary fat, other than consuming more dietary fat, is to increase energy expenditure by an increase of physical activity. Indeed, there are indications that physical activity is an important determinant of fat oxidation. Based on the evidence presented, it is concluded that the obesity epidemic is mainly due to a high dietary intake, especially as fat, and that physical activity can be a tool to modulate the effect of fat intake on body fat.     

Trends for weight control strategies in Korean adults using the Korea National Health and Nutrition Examination Survey from 2007 to 2017

BackgroundObesity is an increasing global health problem and is associated with various diseases including stroke, respiratory diseases, diabetes mellitus, and hypertension. Various weight control strategies such as exercise, calorie-restricted diet, anti-obesity medication, herbal medicine, and functional food are being used. The present study aimed to investigate the trends of weight control strategies in Korean adultsMethodsThis was a cross-sectional study that used data from the Korea National Health and Nutrition Examination Survey from 2007 to 2017. A total of 64,207 participants were analyzed. The body mass index (BMI), subjective judgment of body appearance, practice of weight control, and methods to control weight were analyzed according to year and sex.ResultsThe prevalence rate of obesity in men based on a BMI of 25 or higher was slightly increased from 37.0% in 2007 to 41.1% in 2017. Among the weight control strategies, use of exercise decreased from 83.8% to 80.5% in men, and from 73.4% to 69.5% in women, reduction in the amount of food consumed increased from 47.1% to 60.5% in men and from 65.1% to 70.6% in women, consumption of functional food increased from 3% to 6.2% in men and from 3.2% to 8.7% in women, and rate of skipping meals increased from 6.1% to 12.0% in men and from 11.5% to 14.0% in women.ConclusionThe present study showed that exercise has decreased and dietary control and functional food consumption have increased as weight control strategies in Korean adults during the past decade.