Self-selected Food Intake Research Articles

Sleep and meal timing influence food intake and its hormonal regulation in healthy adults with overweight/obesity.

Studies associate sleeping and eating late in the day with poor dietary quality and higher obesity risk but differences in sleep duration confound this association. We aimed to determine whether sleep and meal timing, independent of sleep duration, influenced food intake in healthy adults. This was a controlled, 2 × 2 inpatient crossover study with normal (0000-0800 h) or late (0330-1130 h) sleep and normal (1, 5, 11, and 12.5 h after awakening) or late (4.5, 8.5, 14.5, and 16 h after awakening) meals. Food intake was controlled while blood samples were obtained for determination of appetite-regulating hormones on days 3-4. Self-selected food intake was assessed on day 5. Data were analyzed using linear mixed model analysis with sleep, meal, and sleep x meal interaction as dependent variables. Five participants completed all phases (mean age 25.1 ± [SD] 3.9 y, body mass index 29.2 ± 2.7 kg/m2). There was a significant sleep x meal interaction on energy intake (P = 0.035) and trends on fat and sodium intakes (P < 0.10). Overnight ghrelin concentrations were higher under normal sleep and meal conditions relative to late (P < 0.005) but lower when both were combined (P < 0.001). Overnight leptin concentrations were higher under normal meal conditions (P = 0.012). There was a significant sleep x meal interaction on ghrelin (P = 0.032) and glucagon-like peptide 1 (P = 0.041) concentrations, but not leptin (P = 0.83), in response to a test meal. Our results suggest that alignment of sleep and meals may influence food choice and energy balance. Additional research is necessary to expand and confirm our findings.

Evidence for Efficacy and Effectiveness of Changes in Eating Frequency for Body Weight Management

In self-reported diets of free living individuals, frequent eating is associated with higher energy intake, yet beliefs about the possible beneficial effect of higher eating frequency for managing body weight persist. Prospective cohort studies and controlled trials of manipulation of eating frequency published by 31 December 2012 were reviewed to assess whether variation in eating frequency may be an adjunct to weight management. Four prospective cohort studies were identified; 2 of these included adults followed for 10 y and 2 followed pre-adolescent/adolescent girls for 6 or 10 y. Within each age category, the findings of the 2 studies were contradictory. Six controlled trials with adult subjects serving as their own controls found no significant changes in body weight due to manipulation of eating frequency interventions lasting 6-8 wk. In 6 additional intervention trials of 8-52 wk duration, free-living adults were counseled to change the eating frequency of self-selected food intake with no significant differences in weight loss attributable to eating frequency. Overall, the consistency of the null findings from controlled trials of manipulation of eating frequency for promoting weight loss suggests that beliefs about the role of higher eating frequency in adult weight management are not supported by evidence. Interpretation of the evidence from published observational studies is complicated by differences in definition of eating frequency and limited knowledge of systematic and random errors in measurement of eating frequency.

Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults

BackgroundThe ability of modified alternate-day fasting (ADF; ie, consuming 25% of energy needs on the fast day and ad libitum food intake on the following day) to facilitate weight loss and lower vascular disease risk in obese individuals remains unknown. ObjectiveThis study examined the effects of ADF that is administered under controlled compared with self-implemented conditions on body weight and coronary artery disease (CAD) risk indicators in obese adults. DesignSixteen obese subjects (12 women, 4 men) completed a 10-wk trial, which consisted of 3 phases: 1) a 2-wk control phase, 2) a 4-wk weight loss/ADF controlled food intake phase, and 3) a 4-wk weight loss/ADF self-selected food intake phase. ResultsDietary adherence remained high throughout the controlled food intake phase (days adherent: 86%) and the self-selected food intake phase (days adherent: 89%). The rate of weight loss remained constant during controlled food intake (0.67 ± 0.1 kg/wk) and self-selected food intake phases (0.68 ± 0.1 kg/wk). Body weight decreased (P < 0.001) by 5.6 ± 1.0 kg (5.8 ± 1.1%) after 8 wk of diet. Percentage body fat decreased (P < 0.01) from 45 ± 2% to 42 ± 2%. Total cholesterol, LDL cholesterol, and triacylglycerol concentrations decreased (P < 0.01) by 21 ± 4%, 25 ± 10%, and 32 ± 6%, respectively, after 8 wk of ADF, whereas HDL cholesterol remained unchanged. Systolic blood pressure decreased (P < 0.05) from 124 ± 5 to 116 ± 3 mm Hg. ConclusionThese findings suggest that ADF is a viable diet option to help obese individuals lose weight and decrease CAD risk. This trial was registered at clinicaltrials.gov as UIC-004-2009.

Evaluation of high-protein supplementation in weight-stable HIV-positive subjects with a history of weight loss: a randomized, double-blind, multicenter trial

Background:HIV patients with wasting are at increased risk of opportunistic complications and fatality. Objective:We hypothesized that augmenting dietary intake with high-biologic-value protein would enhance weight and lean tissue in weight-stable subjects with a prior unintentional weight loss of >3%. Design:Fifty-nine subjects with HIV RNA concentrations <5000 copies/mL were randomly assigned to receive a 280-kcal supplement containing 40 g whey protein or a matched isocaloric control supplement without added protein twice daily for 12 wk. Results:Before the study, intake of total energy and protein exceeded estimated requirements (44.3 ± 12.6 kcal · kg−1 · d−1 and 1.69 ± 0.55 g · kg−1 · d−1, respectively). Both supplements failed to increase total energy intake because of decreases in self-selected food intake. Changes in weight (0.8 ± 2.4 and 0.7 ± 2.4 kg) and lean body mass (0.3 ± 1.4 and 0.3 ± 1.5 kg) did not differ significantly between the whey protein and control groups, respectively. Waist-to-hip ratio improved more with whey protein (−0.02 ± 0.05) than with the control (0.01 ± 0.03; P = 0.025) at week 6 but not at week 12. Fasting triacylglycerol increased by 39 ± 98 mg/dL with the control supplement and decreased by 16 ± 62 mg/dL with whey protein at week 12 (P = 0.03). CD4 lymphocytes increased by 31 ± 84 cells/mm3 with whey protein and decreased by 5 ± 124 cells/mm3 with the control supplement at 12 wk (P = 0.03). Gastrointestinal symptoms occurred more often with whey protein. Conclusions:A whey protein supplement did not increase weight or lean body mass in HIV-positive subjects who were eating adequately, but it did increase CD4 cell counts. The control supplement with rapidly assimilable carbohydrate substituted for protein increased cardiovascular disease risk factors. Careful dietary and weight history should be obtained before starting nutritional supplements in subjects with stable weight loss and good viral control.

Dronabinol and marijuana in HIV+ marijuana smokers: acute effects on caloric intake and mood

No studies to date have directly compared the tolerability and efficacy of smoked marijuana and oral dronabinol in HIV(+) marijuana smokers. The aim of this study was to compare dronabinol (0, 10, 20, 30 mg p.o.) and marijuana [0.0, 1.8, 2.8, 3.9% Delta(9)-tetrahydrocannabinol (THC)] in two samples of HIV(+) marijuana smokers: those with (n=15) and those without (n=15) a clinically significant loss of muscle mass (<90% body cell mass/height), which is one component of AIDS wasting. Mood, physical symptoms, self-selected food intake, cardiovascular data, and cognitive task performance were measured before and repeatedly after dronabinol and marijuana administration in eight 7-h sessions. Marijuana and dronabinol were administered in randomized order using a within-subject, staggered, double-dummy design. As compared to placebo, (1) marijuana (1.8, 2.8, 3.9% THC) and the lower dronabinol doses (10, 20 mg) were well tolerated (e.g., few physical symptoms, significant increases in ratings of "good drug effect") in both groups of participants; the highest dose of dronabinol (30 mg) was poorly tolerated in a subset of participants; (2) marijuana and dronabinol significantly increased caloric intake in the low bioelectrical impedance analysis (BIA) group but not in the normal BIA group; and (3) drug effects on cognitive performance were minor. These data suggest that for experienced marijuana smokers with clinically significant muscle mass loss, both dronabinol (at acute doses at least four to eight times the current recommendation) and marijuana produce substantial and comparable increases in food intake without producing adverse effects.

QTL analysis of self-selected macronutrient diet intake: fat, carbohydrate, and total kilocalories.

The present study investigated the inheritance of dietary fat, carbohydrate, and kilocalorie intake traits in an F(2) population derived from an intercross between C57BL/6J (fat-preferring) and CAST/EiJ (carbohydrate-preferring) mice. Mice were phenotyped for self-selected food intake in a paradigm which provided for 10 days a choice between two macronutrient diets containing 78/22% of energy as a composite of either fat/protein or carbohydrate/protein. Quantitative trait locus (QTL) analysis identified six significant loci for macronutrient intake: three for fat intake on chromosomes (Chrs) 8 (Mnif1), 18 (Mnif2), and X (Mnif3), and three for carbohydrate intake on Chrs 17 (Mnic1), 6 (Mnic2), and X (Mnic3). An absence of interactions among these QTL suggests the existence of separate mechanisms controlling the intake of fat and carbohydrate. Two significant QTL for cumulative kilocalorie intake, adjusted for baseline body weight, were found on Chrs 17 (Kcal1) and 18 (Kcal2). Without body weight adjustment, another significant kcal locus appeared on distal Chr 2 (Kcal3). These macronutrient and kilocalorie QTL, with the exception of loci on Chrs 8 and X, encompassed chromosomal regions influencing body weight gain and adiposity in this F2 population. These results provide new insight into the genetic basis of naturally occurring variation in nutrient intake phenotypes.

Preexercise meal composition alters plasma large neutral amino acid responses during exercise and recovery

This study was designed to determine the effect of ingesting three preexercise meals on energy metabolism during exercise and recovery and to relate metabolic perturbations to subjective and objective measurements associated with central fatigue. Twelve subjects consumed isoenergetic meals consisting of oat, wheat, or corn cereals 90 min before cycling. A fasting trial served as the control. Blood samples and cognitive function, perceived hunger, and sleepiness measurements were obtained before and after feeding and during recovery when self-selected food intake was also measured. After meal ingestion, plasma insulin was lower for oat than for wheat or corn whereas the ratio of tryptophan to large neutral amino acids (LNAAs) for corn was less than for all others. During exercise, the tryptophan-LNAA ratio increased from preexercise values for the fasting and wheat trials, but exercise performance was unaffected. During recovery, tryptophan:LNAA increased from postexercise values in fasting trials. Also, hunger and fatigue ratings were greater in fasted subjects, but self-selected food intake measured at the end of the recovery period was not different among groups. We conclude that preexercise meal consumption affected tryptophan:LNAA before, during, and after exercise, but these changes were not sufficient to alter physical and cognitive performance.

Energy balance in an inbred strain of rats: Comparison with the wistar strain

Food intake and body weight gain were examined in two groups of male rats (7 weeks): an inbred strain, Dark Agouti (DA, n = 12) and a noninbred strain, Wistar ( n = 13). The animals were allowed to select their diet from separate sources of the three macronutrients protein, fat, and carbohydrate. After 10 days of adaptation to the diets, body weights and food intakes were measured for 3 weeks. During this period, meal patterns were recorded for at least 5 days in each rat. Then, rats were switched to a chow diet (UAR, A.O4) for 10 days. The total caloric intake of DA rats was 60% that of Wistar rats, while their body weight gain was 25% that of Wistar rats (1.3 g/day in DA vs. 5.3 g in Wistar). However, when energy intake was related to total body weight, there was no difference in energy ingestion. It was observed that DA rats ingested mainly proteins (45%) and fats (41%),while Wistar rats ingested an identical proportion of proteins and carbohydrates (40%). The percent of total white adipose tissue to total body weight was identical in both strains (6% on average). Brown adipose tissue thermogenic activity of DA rats was threefold higher than in Wistar rats. This could be one of the elements responsible for the lower body weight gain of this group of rats. Self-selected food intake of the inbred DA strain of rats, in contrast to what was expected, was greatly variable.

Food intake of very obese persons: Quantitative and qualitative aspects

To document the caloric intake of very obese persons and investigate the food choices and dietary composition that maintain severe obesity, we studied the self-selected food intake required to maintain stable weight in two groups of very obese subjects: 11 inpatients with a mean weight 181% above desirable body weight and 35 outpatients with a mean weight 125% above desirable body weight. Qualitative and quantitative food intake were evaluated using records obtained on the hospital metabolic ward for the inpatients and using self-recorded food records for the outpatients. Absolute caloric intake in both groups was greater in proportion to the degree of obesity (deviation from desirable body weight); caloric intake per unit of lean body mass (kilocalories per gram urinary creatinine) was constant regardless of the degree of obesity and was essentially the same as that of normal nonobese persons. Food records indicated that the obese subjects maintained their high caloric intake by consuming mostly foods of high caloric density, with occasional binge eating. They largely avoided foods of low intrinsic energy density and modified-calorie foods, ie, foods with decreased fat, nonnutritive sweeteners, or fillers. By substituting foods of lower caloric density for usual food choices from the same food group, obese persons could decrease caloric intake by 20% and increase potential for notable weight loss.

The fleece growth of young Lincoln, Corriedale, Polwarth, and fine Merino maiden ewes under housed conditions and unrestricted and progressively restricted feeding on a standard diet.

Two experiments have been conducted with young Lincoln, Corriedale, Polwarth, and fine Merino maiden ewes to compare the growth of fleece by these breeds and to assess relations between the growth of fleece and some factors, nutritional and non-nutritional, likely to influence its growth. In both experiments four representatives of each breed were kept in a sheep house in single pens and fed a high quality diet of constant composition. The second experiment followed immediately on the first and the same sheep were used except for necessary replacements. In the first experiment, which lasted for about one year, the intake of the diet was continuously unrestricted; in the second the intake of the diet was progressively restricted by ordered steps and was finally maintained for 12 weeks at one-fifth of the unrestricted intake of the first 4 weeks of the experiment. With few exceptions, the absolute or relative values of the characters measured formed a smooth series from the fine Merino through the Polwarth and Corriedale to the Lincoln-either in ascending order (e.g. food and water intake; liveweight and chest dimensions; fibre thickness, length, and volume; clean wool, suint, and total skin products output; clean wool and suint output per unit food intake) or descending order (e.g. total and primary follicle density; ratio of secondaries to primaries; wax output and wax output per unit food intake) or showed little or no difference between the breeds (e.g. body length and height; food intake per unit net liveweight; total skin products per unit food intake). The relative positions of the breeds as shown in the first experiment mere generally maintained in the second as food intake was progressively reduced. The results of the two experiments were combined for the individuals and a series of partial regression analyses were undertaken to determine the regression of some variables of fleece production on the level of food intake, atmospheric temperature, fleece weight, and experimental time. Self-selected food intake decreased with increase in fleece weight and less obviously with increase in experimental time (or, possibly, with deposition of subcutaneous fat). Water intake increased with both increase in food intake and rise in atmospheric temperature. Wool weight produced, and fibre thickness, length, and volume growth, all increased with increase in food intake, and within the limits of observed food intake the relation between wool growth and food intake was adequately represented by linear regression. Increase in atmospheric temperature exerted no significant influence on wool growth, except by the Lincolns (through fibre thickness). A positive regression of wool growth rate on fleece weight, acting through fibre length growth, was found, but change in fibre thickness was not related to increase in fleece weight. Wax production was positively related to increase in food intake and negatively to rise in atmospheric temperature. Suint production was positively related to both food intake and fleece weight. Wool, wax and suint production per unit food intake decreased with increase in food intake. Wax per unit food intake decreased with rise in temperature and suint per unit food intake increased with increase in fleece weight.