Genetic risk, body mass index, and weight control behaviors: Unlocking the triad

BACKGROUND

The relationship between genetic risk for body mass index (BMI) and weight control behaviors remains unknown. The objectives of this study were to determine the association between genetic risk for BMI and weight control behaviors in young adults, and to examine actual measured BMI as a potential mediator variable.

METHOD

We analyzed data from three data collection waves of the National Longitudinal Study of Adolescent to Adult Health. The BMI polygenic score (PGS) was based on published genome-wide association studies for BMI. BMI was collected at 11-18 years and 18-26 years. Weight control behaviors included self-reported: (a) weight loss behaviors (dieting, vomiting, fasting/skipping meals, diet pills, laxatives, or diuretic use to lose weight) and (b) weight gain behaviors (eating more or different foods than normal, taking supplements to gain weight).

RESULTS

Among 4,397 participants, the BMI PGS was associated with higher odds of weight loss behaviors in females (OR 1.24, 95% CI 1.14-1.35) and males (OR 1.43, 95% CI 1.26-1.62), and this association was mediated by BMI (indirect effect 0.04, 95% CI 0.03-0.05 in females and 0.03, 95% CI 0.03-0.04 in males). The BMI PGS was associated with lower odds of weight gain behaviors in females and males, which was also mediated by actual BMI.

CONCLUSIONS

The BMI PGS was associated with weight loss behaviors in both males and females, and this association was mediated by actual measured BMI. Clinical interventions to prevent high BMI, particularly for individuals with genetic risk, may also prevent subsequent development of potentially unhealthy weight loss behaviors.

Boys, Bulk, and Body Ideals: Sex Differences in Weight-Gain Attempts Among Adolescents in the United States

OBJECTIVE

To determine the prevalence of weight-gain attempts in adolescent boys in the United States.

METHODS

Participants were 15,624 high school students from the nationally representative 2015 Youth Risk Behavior Survey.

RESULTS

Overall, 29.6% of adolescent boys reported attempts to gain weight, including 39.6% of boys who were normal weight, 12.8% who were overweight, and 10.6% who were obese by body mass index (BMI). In contrast, only 6.5% of adolescent girls reported attempts to gain weight. Although only 3.3% of adolescent males are underweight by BMI, 19.3% perceive themselves to be underweight. Further, over half of adolescent males who are overweight by BMI perceive themselves to be about the right weight. Black/African-American (odds ratio [OR] 1.89; 95% confidence interval [CI] 1.50-2.38) and multiracial (OR 1.62; 95% CI 1.16-2.26) adolescent males had greater odds of weight-gain attempts than white adolescent males. Adolescent males identifying as bisexual had lower odds (OR .47; 95% CI .25-.88) of weight-gain attempts than adolescent males identifying as heterosexual.

CONCLUSIONS

Weight-gain attempts are common among adolescent boys including those who are considered normal weight, overweight, or obese by BMI; African-American or multiracial; and those self-identifying as heterosexual. Consideration of the unique nature of male body image, particularly adolescent boys' perceptions of their own weight and weight-gain attempts, should be incorporated into primary care screening for adolescent boys.

Weight restoration in atypical anorexia nervosa: A clinical conundrum

The determination of the treatment goal weight for adolescents with a restrictive eating disorder (ED) and a prior history of obesity, such as in atypical anorexia nervosa (AAN), represents an ongoing challenge for clinicians. This determination is particularly complex given competing interests of physical recovery from significant weight loss, mental recovery from ED psychopathology, and the medical comorbidities associated with obesity. We report the case of a 15-year old female with a history of obesity and irregular periods who presented with significant weight loss and absence of menses for 3 months. She was hospitalized for severe malnutrition and bradycardia, initiated family based treatment, and regained periods. However, her vital sign instability and eating disorder cognitions did not resolve until she reached a weight at which point her periods again ceased due to polycystic ovary syndrome. This case highlights the need for regular monitoring during weight recovery and the clinical challenge of determining the treatment goal weight in adolescents with EDs and prior obesity.

Differential Risk Factors for Unhealthy Weight Control Behaviors by Sex and Weight Status Among U.S. Adolescents

PURPOSE

To determine if previously reported risk factors for the development of unhealthy weight control behaviors differ by sex and weight status using a nationally representative longitudinal sample of adolescents followed through young adulthood.

METHODS

We used nationally representative longitudinal cohort data collected from baseline (11-18 years old, 1994-1995, Wave I) and seven-year follow-up (18-24 years old, 2001-2002, Wave III) of the National Longitudinal Study of Adolescent to Adult Health (Add Health). We examined potential risk factors (adverse childhood events and adolescent family, school, body image, and mental health factors) for the development of unhealthy weight control behaviors including vomiting, fasting/skipping meals, or laxative/diuretic use to lose weight at seven-year follow-up in young adulthood.

RESULTS

Of the 14,322 included subjects, 11% reported unhealthy weight control behavior at follow-up in young adulthood, with the highest proportion (23.7%) among overweight/obese females and the lowest proportion (3.7%) among underweight/normal weight males. All adolescent family factors were significantly associated with unhealthy weight control behaviors in underweight/normal weight females, whereas none were significantly associated in overweight/obese males. Similar trends were noted for adverse childhood events, and adolescent school and community factors. Adolescent self-perception of being overweight was associated with young adult unhealthy weight control behaviors among all subgroups.

CONCLUSIONS

Risk factors for unhealthy weight control behaviors may differ based on sex and weight status. Screening, prevention, and treatment interventions for unhealthy weight control behaviors in adolescents and young adults may need to be tailored based on sex and weight status.

Disordered eating behaviors and cardiometabolic risk among young adults with overweight or obesity

OBJECTIVE

To determine if unhealthy weight control behaviors or binge-eating behaviors among young adults with overweight/obesity are associated with body mass index (BMI) change and cardiometabolic risk at 7-year follow-up.

METHODS

We used longitudinal cohort data from 5,552 young adults with overweight/obesity at baseline (18-24 years) with 7-year follow-up (24-32 years) from the National Longitudinal Study of Adolescent to Adult Health. Baseline predictors were: (a) unhealthy weight control behaviors such as vomiting, fasting, skipping meals, or laxative/diuretic use to lose weight; or (b) binge-eating behaviors. Participants reporting either unhealthy weight control behaviors or binge-eating behaviors were considered to engage in any disordered eating behavior (DEB). Outcomes at 7-year follow-up were BMI change, incident diabetes, incident hypertension, and incident hyperlipidemia.

RESULTS

Young adults with overweight/obesity reporting unhealthy weight control behaviors at baseline had higher BMI and weight at 7-year follow-up than those without unhealthy weight control behaviors. In regression models adjusting for baseline BMI, race/ethnicity, age, and education, unhealthy weight control behaviors were associated with greater change in BMI in both sexes and binge-eating behavior at baseline was associated with greater odds of incident hyperlipidemia (odds ratio 1.90, 95% CI 1.29-2.79) at 7-year follow-up in males.

CONCLUSIONS

The higher risk for increased BMI (in both males and females) and incident hyperlipidemia (in males) over time in young adults with overweight/obesity who engage in DEBs underscores the need to screen for DEBs in this population and provide referrals and tailored interventions as appropriate.

Prevalence and Correlates of Disordered Eating Behaviors Among Young Adults with Overweight or Obesity

BACKGROUND

Clinical and community samples indicate that eating disorders (EDs) and disordered eating behaviors (DEBs) may co-occur among adolescents and young adults at a weight status classified as overweight or obese.

OBJECTIVE

To determine the prevalence of EDs and DEBs among young adults at a weight status classified as overweight or obese using a nationally representative sample and to characterize differences in prevalence by sex, race/ethnicity, sexual orientation, and socioeconomic status.

DESIGN

Cross-sectional nationally representative data collected from Wave III of the National Longitudinal Study of Adolescent to Adult Health (Add Health).

PARTICIPANTS

Young adults ages 18-24 years old.

MAIN MEASURES

ED diagnosis and DEBs (self-reported binge eating or unhealthy weight control behaviors including vomiting, fasting/skipping meals, or laxative/diuretic use to lose weight). Covariates: age, sex, race/ethnicity, sexual orientation, weight status, and education.

KEY RESULTS

Of the 14,322 young adults in the sample, 48.6% were at a weight status classified as overweight or obese. Compared to young adults at a weight status classified as underweight or normal weight, those at a weight status classified as overweight or obese reported a higher rate of DEBs (29.3 vs 15.8% in females, 15.4 vs 7.5% in males). Logistic regression analyses demonstrated that odds of engaging in DEBs were 2.32 (95% confidence interval 2.05-2.61) times higher for females compared to males; 1.66 (1.23-2.24) times higher for Asian/Pacific Islander compared to White; 1.62 (1.16-2.26) times higher for homosexual or bisexual compared to heterosexual; 1.26 (1.09-1.44) times higher for high school or less versus more than high school education; and 2.45 (2.16-2.79) times higher for obesity compared to normal weight, adjusting for all covariates.

CONCLUSIONS

The high prevalence of DEBs particularly in young adults at a weight status classified as overweight or obese underscores the need for screening, referrals, and tailored interventions for DEBs in this population.

History of Overweight/Obesity as Predictor of Care Received at 1-year Follow-Up in Adolescents With Anorexia Nervosa or Atypical Anorexia Nervosa

PURPOSE

Previous research has indicated that patients with anorexia nervosa (AN) or atypical AN with premorbid history of overweight/obesity have greater weight loss and longer illness duration than patients with no such history. However, little is known about the association of premorbid overweight/obesity and receiving inpatient medical care during treatment for an eating disorder.

METHODS

Using logistic regression, we sought to determine if history of overweight/obesity was associated with receiving inpatient medical care in a sample of 522 patients (mean age 15.5 years, 88% female) with AN/atypical AN.

RESULTS

Binary results demonstrated greater percent weight loss (27.4% vs. 16.2%) and higher percent median body mass index (%mBMI, 99.8% vs. 85.2%) at presentation in those with a history of overweight/obesity (p < .001) but no difference in duration of illness (p = .09). In models adjusted for demographics and percent weight loss, history of overweight/obesity was associated with lower odds of receiving inpatient medical care (odds ratio .60 [95% confidence interval: .45-.80]) at 1-year follow-up. However, these associations were no longer significant after adjusting for %mBMI. Mediation results suggest that %mBMI fully mediates the relationship between history of overweight/obesity and inpatient medical care, in that those with a history of overweight/obesity are less likely to receive care due to presenting at a higher weight.

CONCLUSIONS

Our findings suggest that, despite greater degree of weight loss and no difference in duration of illness, participants with a history of overweight/obesity are less likely to receive inpatient medical care.

A systematic review of approaches to refeeding in patients with anorexia nervosa

OBJECTIVE

Given the importance of weight restoration for recovery in patients with anorexia nervosa (AN), we examined approaches to refeeding in adolescents and adults across treatment settings.

METHODS

Systematic review of PubMed, PsycINFO, Scopus, and Clinical Trials databases (1960-2015) using terms refeeding, weight restoration, hypophosphatemia, anorexia nervosa, anorexia, and anorexic.

RESULTS

Of 948 screened abstracts, 27 met these inclusion criteria: participants had AN; reproducible refeeding approach; weight gain, hypophosphatemia or cognitive/behavioral outcomes. Twenty-six studies (96%) were observational/prospective or retrospective and performed in hospital. Twelve studies published since 2010 examined approaches starting with higher calories than currently recommended (≥1400 kcal/d). The evidence supports 8 conclusions: 1) In mildly and moderately malnourished patients, lower calorie refeeding is too conservative; 2) Both meal-based approaches or combined nasogastric+meals can administer higher calories; 3) Higher calorie refeeding has not been associated with increased risk for the refeeding syndrome under close medical monitoring with electrolyte correction; 4) In severely malnourished inpatients, there is insufficient evidence to change the current standard of care; 5) Parenteral nutrition is not recommended; 6) Nutrient compositions within recommended ranges are appropriate; 7) More research is needed in non-hospital settings; 8) The long-term impact of different approaches is unknown;

DISCUSSION

Findings support higher calorie approaches to refeeding in mildly and moderately malnourished patients under close medical monitoring, however the safety, long-term outcomes, and feasibility outside of hospital have not been established. Further research is also needed on refeeding approaches in severely malnourished patients, methods of delivery, nutrient compositions and treatment settings.

Update on the medical management of eating disorders in adolescents

The medical practitioner has an important role to play in the management of adolescents with eating disorders, usually as part of a multidisciplinary team. This article reviews the role of the medical practitioner in the diagnosis and treatment of eating disorders, updating the reader on the changing epidemiology of eating disorders, revised diagnostic criteria, newer methods of assessing degree of malnutrition, more aggressive approaches to refeeding, and current approaches to managing low bone mass.

Refeeding hypophosphatemia in hospitalized adolescents with anorexia nervosa: a position statement of the Society for Adolescent Health and Medicine

Refeeding hypophosphatemia in hospitalized adolescents with anorexia nervosa is correlated with degree of malnutrition. Therefore, when initiating nutritional rehabilitation, clinicians should have a heightened awareness of the possibility of refeeding hypophosphatemia in severely malnourished patients (<70% median body mass index).

Is fast food addictive?

Studies of food addiction have focused on highly palatable foods. While fast food falls squarely into that category, it has several other attributes that may increase its salience. This review examines whether the nutrients present in fast food, the characteristics of fast food consumers or the presentation and packaging of fast food may encourage substance dependence, as defined by the American Psychiatric Association. The majority of fast food meals are accompanied by a soda, which increases the sugar content 10-fold. Sugar addiction, including tolerance and withdrawal, has been demonstrated in rodents but not humans. Caffeine is a "model" substance of dependence; coffee drinks are driving the recent increase in fast food sales. Limited evidence suggests that the high fat and salt content of fast food may increase addictive potential. Fast food restaurants cluster in poorer neighborhoods and obese adults eat more fast food than those who are normal weight. Obesity is characterized by resistance to insulin, leptin and other hormonal signals that would normally control appetite and limit reward. Neuroimaging studies in obese subjects provide evidence of altered reward and tolerance. Once obese, many individuals meet criteria for psychological dependence. Stress and dieting may sensitize an individual to reward. Finally, fast food advertisements, restaurants and menus all provide environmental cues that may trigger addictive overeating. While the concept of fast food addiction remains to be proven, these findings support the role of fast food as a potentially addictive substance that is most likely to create dependence in vulnerable populations.

A prospective examination of weight gain in hospitalized adolescents with anorexia nervosa on a recommended refeeding protocol

PURPOSE

Current refeeding recommendations for adolescents hospitalized with anorexia nervosa (AN) are conservative, starting with low calories and advancing slowly to avoid refeeding syndrome. The purpose of this study was to examine weight change and clinical outcomes in hospitalized adolescents with AN on a recommended refeeding protocol.

METHODS

Adolescents aged 13.1-20.5 years were followed during hospitalization for AN. Weight, vital signs, electrolytes, and 24-hour fluid balance were measured daily. Percent median body mass index (%MBMI) was calculated as 50th percentile BMI for age and gender. Calories were prescribed on admission and were increased every other day.

RESULTS

Thirty-five subjects with a mean (SD) age of 16.2 (1.9) years participated over 16.7 (6.4) days. Calories increased from 1,205 (289) to 2,668 (387). No subjects had refeeding syndrome; 20% had low serum phosphorus. Percent MBMI increased from 80.1 (11.5) to 84.5 (9.6); overall gain was 2.10 (1.98) kg. However, 83% of subjects initially lost weight. Mean %MBMI did not increase significantly until day 8. Higher calories prescribed at baseline were significantly associated with faster weight gain (p = .003) and shorter hospital stay (p = .030) in multivariate regression models adjusted for %MBMI and lowest heart rate on admission.

CONCLUSIONS

Hospitalized adolescents with AN demonstrated initial weight loss and slow weight gain on a recommended refeeding protocol. Higher calorie diets instituted at admission predicted faster weight gain and shorter hospital stay. These findings support the development of more aggressive feeding strategies in adolescents hospitalized with AN. Further research is needed to identify caloric and supplementation regimens to maximize weight gain safely while avoiding refeeding syndrome.

Does delivering preventive services in primary care reduce adolescent risky behavior?

PURPOSE

To determine whether the delivery of preventive services changes adolescent behavior. This exploratory study examined the trajectory of risk behavior among adolescents receiving care in three pediatric clinics, in which a preventive services intervention was delivered during well visits.

METHODS

The intervention consisted of screening and brief counseling from a provider, followed by a health educator visit. At age 14 (year 1), 904 adolescents had a risk assessment and intervention, followed by a risk assessment 1 year later at age 15 (year 2). Outcomes were changes in adolescent behavior related to seat belt and helmet use; tobacco, alcohol, and drug use; and sexual behavior. Analysis involved age-related comparisons between the intervention and several cross-sectional comparison samples from the age of 14-15 years.

RESULTS

The change in helmet use in the intervention sample was 100% higher (p < .05), and the change in seat belt use among males was 50% higher (p = .14); the change in smoking among males was 54% lower (p < .10), in alcohol use was no different, and in drug use was 10% higher (not significant [NS]); and the change in rate of sexual intercourse was 18% and 22% lower than cohort comparison samples (NS).

CONCLUSIONS

The intervention had the strongest effect in the area of helmet use, shows promise for increasing seat belt use and reducing smoking among male adolescents, and indicates a nonsignificant trend toward delaying the onset of sexual activity. Participation in the intervention seemed to have no effect on the rates of experimentation with alcohol and drugs between the ages of 14 and 15 years.

Contribution of pollinator-mediated crops to nutrients in the human food supply

The contribution of nutrients from animal pollinated world crops has not previously been evaluated as a biophysical measure for the value of pollination services. This study evaluates the nutritional composition of animal-pollinated world crops. We calculated pollinator dependent and independent proportions of different nutrients of world crops, employing FAO data for crop production, USDA data for nutritional composition, and pollinator dependency data according to Klein et al. (2007). Crop plants that depend fully or partially on animal pollinators contain more than 90% of vitamin C, the whole quantity of Lycopene and almost the full quantity of the antioxidants β-cryptoxanthin and β-tocopherol, the majority of the lipid, vitamin A and related carotenoids, calcium and fluoride, and a large portion of folic acid. Ongoing pollinator decline may thus exacerbate current difficulties of providing a nutritionally adequate diet for the global human population.

A clinic-based lifestyle intervention for pediatric obesity: efficacy and behavioral and biochemical predictors of response

AIM

To examine efficacy and predictors of response to a lifestyle intervention for obese youth.

METHODS

Retrospective chart review of 214 children and adolescents aged 8-19 years. Linear regression identified baseline predictors of response (delta BMI z-score) at first and ultimate follow-up visits.

RESULTS

Mean delta BMI z-score from baseline was -0.04 (p < 0.001) at first follow-up and -0.09 (p < 0.001) at ultimate follow-up (median time 10 mo) among 156 children and adolescents. Higher baseline BMI z-score predicted poor response at first and ultimate follow-up, explaining 10% of variance in response. Fasting insulin explained 6% of response variance at first follow-up. delta BMI z-score at the first visit along with baseline BMI z-score explained up to 50% of variance in response at ultimate visit.

CONCLUSION

Clinic-based interventions improve weight status. Baseline variables predict only a small proportion of response; response at the first visit is a more meaningful tool to guide clinical decisions.

Body mass index and disordered eating behaviors are associated with weight dissatisfaction in adolescent and young adult female military recruits

OBJECTIVE

To examine factors associated with weight dissatisfaction, a risk factor for eating disorders, among female Marine recruits.

METHODS

A diverse adolescent/young adult sample of 2157 female recruits completed a questionnaire upon entering Marine Corps training. Weight dissatisfaction was the main variable of interest.

RESULTS

Body mass index (BMI), disordered eating history, and worry about meeting military "weight" were related highly to weight dissatisfaction. Women with BMIs near the upper limit of the Marine Corps weight standard (23.5 kg/m2) reported the highest rates of weight dissatisfaction. Those who reported vomiting, binging or pill use, or being worried about "making weight" were four and five times, respectively, more likely to report weight dissatisfaction.

CONCLUSIONS

New female Marine recruits with higher BMIs, disordered eating histories, and worries about "making weight" are significantly more likely to be weight dissatisfied. Such findings may identify those at risk for developing eating disorders when exposed to strict military weight standards.

Increasing the screening and counseling of adolescents for risky health behaviors: a primary care intervention

OBJECTIVE

To determine whether a systems intervention for primary care providers resulted in increased preventive screening and counseling of adolescent patients, compared with the usual standard of care.

METHODS

The intervention was conducted in 2 outpatient pediatric clinics; 2 other pediatric clinics in the same health maintenance organization served as comparison sites. The intervention was implemented in 2 phases: first, pediatric primary care providers attended a training workshop (N = 37) to increase screening and counseling of adolescents in the areas of tobacco, alcohol, drugs, sexual behavior, and safety (seatbelt and helmet use). Second, screening and charting tools were integrated into the intervention clinics. Providers in the comparison sites (N = 39) continued to provide the usual standard of care to their adolescent patients. Adolescent reports were used to assess changes in provider behavior. After a well visit, 13- to 17-year olds (N = 2628) completed surveys reporting on whether their provider screened and counseled them for risky behavior.

RESULTS

Screening and counseling rates increased significantly in each of the 6 areas in the intervention sites, compared with rates of delivery using the usual standard of care. Across the 6 areas combined, the average screening rate increased from 58% to 83%; counseling rates increased from 52% to 78%. There were no significant increases in the comparison sites during the same period. The training component seems to account for most of this increase, with the tools sustaining the effects of the training.

CONCLUSIONS

The study offers strong support for an intervention to increase clinicians' delivery of preventive services to a wide age range of adolescent patients.

Comparison of phylloquinone bioavailability from food sources or a supplement in human subjects

Phylloquinone (K) absorption was assessed in 22- to 30-y-old human subjects consuming a standard test meal [402 kcal (1682 kJ), 27% energy from fat]. The absorption of phylloquinone, measured over a 9-h period as the area under the curve (AUC), was higher (P < 0.01) after the consumption of a 500- microgram phylloquinone tablet [27.55 +/- 10.08 nmol/(L. h), n = 8] than after the ingestion of 495 microgram phylloquinone as 150 g of raw spinach [4.79 +/- 1.11 nmol/(L. h), n = 3]. Less phylloquinone (P < 0.05) was absorbed from 50 g of spinach (AUC = 2.49 +/- 1.11 nmol/(L. h) than from 150 g of spinach. Absorption of phylloquinone from fresh spinach (165 microgram K), fresh broccoli (184 microgram K) and fresh romaine lettuce (179 microgram K) did not differ. There was no difference in phylloquinone absorption from fresh or cooked broccoli or from fresh romaine lettuce consumed with a meal containing 30 or 45% energy as fat.

Effect of theophylline on ventilatory roll-off during hypoxia in goats

The increase in pulmonary ventilation (VE) during the first minutes of hypoxia is not sustained as after several minutes VE decreases or "rolls-off" toward control levels. We hypothesized that intravenous infusion of theophylline, by blocking the central inhibitory effects on breathing of adenosine, would attenuate the hypoxic VE roll-off. Twelve unanesthetized adult goats were exposed for 20 min to a 12% O2-88% N2 gas mixture. In some studies,theophylline was infused intravenously (IV) for 20 min before and during the hypoxia. The highest infusion rate of 6.0--8.0 mg/min was sufficient to totally prevent the arterial hypertension and bradycardia that occurred with IV infusion of 4 mg min (-1) of adenosine. Nine of the 12 goats demonstrated VE roll-off without the theophylline infusion. In goats that demonstrated VE roll-off without theophylline, a significant (P < 0.05) VE roll-off was observed even at the highest theophylline infusion rate. We therefore conclude that the VE roll-off during hypoxia is not primarily or critically mediated by adenosine in awake, adult goats.

Effect of metabolic rate on ventilatory roll-off during hypoxia

This study was done to determine 1) whether goats demonstrate the roll-off phenomenon, i.e., a secondary decrease in minute ventilation (VE), after an initial hyperventilation during various levels of hypoxia and, if so, 2) whether roll-off could be due to changes in metabolic rate. We hypothesized that roll-off occurs in the goat during hypoxia but is not due to hypometabolism. To answer question 1, eight unanesthetized adult goats were exposed to 15-20 min of hypoxia at 0.15, 0.12, and 0.09 inspired O2 fraction (FIO2), resulting in 60, 40, and 30 Torr arterial PO2, respectively. Goats were fitted with a face mask connected to a spirometer to measure VE, and arterial blood gas samples were obtained via carotid arterial catheters. Roll-off was seen with 0.15 and 0.12 FIO2, whereas VE steadily increased with 0.09 FIO2. During hypoxia, arterial PCO2 fell 2, 3, and 7 Torr at 0.15, 0.12, and 0.09 FIO2, respectively. In the second series of experiments, nine different goats were exposed to 30 min of 0.12 FIO2. O2 consumption and CO2 production were measured five times during baseline and hypoxia. VE increased to 32% above baseline values after 2 min of hypoxia and then gradually decreased by 18%. Changes in breathing frequency and tidal volume contributed to the roll-off. O2 consumption decreased (P = 0.0029, analysis of variance) and CO2 production increased (P = 0.0027) during hypoxia, although both changes were small (< 7%) compared with the eventual 18% decrease in VE. We conclude that the adult goat demonstrates the roll-off phenomenon during moderate levels of hypoxia. (ABSTRACT TRUNCATED AT 250 WORDS)