Food Intake Response to Short-Term Modifications of Metabolism in Humans

More than 30% of adults are considered overweight. In general, lifestyle changes (diet and exercise) or current weight loss drugs only lead to about 5 to 10% weight loss. This may be because a person's energy expenditure, aka the number of calories the body uses, leads to hunger and may increase the amount of food a person eats. Cold exposure is known to increase metabolism but it may not lead to weight loss if appetite and the desire for food are also increased. The primary goal of this study is to evaluate whether changing energy expenditure by cool temperature exposure results in changes in food intake. This study will involve a stay on our clinical research unit where we will determine the energy requirements (at 24 degree C) of 68 healthy, adult volunteers without evidence of diabetes. Exposure to cool temperatures (19 degree C) will be used to increase the number of calories a person's body uses in a day. Participants will spend 24 hours in a room that measures energy expenditure while the temperature in the room is turned down, once with a fixed diet (eucaloric) and once with a buffet of food choices (ad libitum). After the fixed diet, volunteers will self-select how much food they wish to eat for one day from a vending machine. Volunteers will also spend one day fasting followed by a day self-selecting their food from the vending machine. Findings from this study will provide knowledge about a possible causal link between energy expenditure and eating behavior. This information may shed light on why many weight loss interventions that increase energy expenditure do not work as well as expected, and may eventually lead to new weight loss approaches and therapies.

• INCLUSION CRITERIA:
• Premenopausal women and men <55 years of age
• Body weight <204 kg (<450 pounds) and >= 36 kg (>= 80 pounds)
• Stable weight (+/-5% within past 6 months) as determined by volunteer report
• Healthy, as determined by medical history, physical examination, and laboratory tests

Exclusion criteria

• Age <18 years
• Weight greater than or equal to 204 kg (greater than or equal to 450 pounds, maximum weight of the iDXA machine as per manufacturer s manual), or weight <36 kg (<80 pounds, minimum weight allowed based on the NIH guidelines of blood drawing for research purposes)
• Use of medications affecting metabolism and appetite in the last three months
• Expresses unwillingness to consume all food given during the weight maintaining diet portions of the study (e.g., due to strict dietary restrictions including allergies or vegetarian or kosher diet)
• Current use of tobacco products, marijuana, amphetamines, cocaine, or intravenous drug use
• Current pregnancy, pregnancy within the past 6 months or lactation
• History or clinical manifestation of:

• Type 1 and Type 2 diabetes mellitus
• History of surgery for the treatment of obesity
• Endocrine disorders, such as Cushing s disease, pituitary disorders, and hypo and hyperthyroidism
• Pulmonary disorders, including chronic obstructive pulmonary disease
• Cardiovascular diseases, including coronary heart disease, heart failure, arrhythmias, and peripheral artery disease
• High blood pressure by sitting blood pressure measurement using an appropriate cuff higher than 140/90 mmHg on two or more occasions, or current antihypertensive therapy
• Liver disease, including cirrhosis, active hepatitis B or C, and AST or ALT greater than or equal to 2x normal
• Gastrointestinal disease including Crohn s disease, ulcerative colitis, celiac disease or other malabsorptive disorders
• Abnormal kidney function (eGFR <60 mL/min/1.73m(2))
• Central nervous system disease, including previous history of cerebrovascular accidents, dementia, neurodegenerative disorders or history of severe head trauma
• Cancer requiring treatment in the past five years, except for nonmelanoma skin cancers or cancers that have clearly been cured
• Infectious disease such as active tuberculosis, HIV (by self report), chronic coccidiomycoses or other chronic infections that might influence EE and weight
• Diagnosis of binge eating disorder, anorexia and major psychiatric disorders based upon the DSM-IV including depression, schizophrenia and psychosis, which may impact the ability of the participant to be in the respiratory chamber for 24 hour time periods
• Chronic ethanol use (more than 3 drinks/day)