Effects of Positive Energy Balance and Exercise on Appetite Hormones in Sedentary Men and Women
Condition: Appetite and General Nutritional Disorders
MeSH terms: Nutrition Disorders
Study type: Interventional

Summary: 
      The purpose of this research study is to examine the effects of overfeeding and exercise on
      blood levels of hormones associated with regulating appetite, also thought of as feelings of
      hunger and satiety (fullness). Previous studies have shown that non-obese people have
      different amounts of these hormones in their blood compared to obese people.

      The investigators hypothesize that exercise will promote improved insulin sensitivity and
      corresponding beneficial changes in obese individuals. The investigators predict exercise
      induced changes in 24-hour plasma hormone levels will be associated with improved appetite
      during overfeeding in obese individuals.
    

Detailed description: 
      In a randomized cross-over design, participants will complete two separate six-day & seven
      night inpatient stays (separated by at least 4 weeks) at the University of Wisconsin
      Hospital's Clinical and Translational Research Core (CTRC). During each six-day & seven night
      visit, participants will be fed an energy balance diet (energy intake = energy expenditure)
      for the first three days followed by three days of overfeeding (130% of the energy balance
      diet). During one of the inpatient periods, participants will exercise twice daily (once in
      the morning, once in the evening) for a total of approximately 120 minutes per day on an
      indoor exercise bicycle at ~50% of maximal aerobic fitness. During the other inpatient visit,
      participants will not exercise and will be inactive.

      The investigators will examine the effect of short-term positive energy balance and exercise
      on 24-hour plasma levels of hormones related to hunger and satiety. These hormones include
      leptin, ghrelin, insulin, and peptide YY in sedentary lean and obese men and women. Our
      primary hypothesis is that when an obese person exercises, average 24-hour plasma leptin
      levels will increase in obese individuals during overfeeding compared to energy balance
      feeding, but fail to do so under sedentary conditions. In contrast, the investigators predict
      lean individuals will have an appropriate increase in average 24-hour leptin levels in
      response to overfeeding regardless of exercise treatment. Thus, the investigators suggest
      that a failure in the average 24-hour leptin response to overfeeding sets an obese person up
      for continued slow weight gain, as the leptin hunger signal fails to detect short-term
      overfeeding and does not produce a response. The investigators hypothesize that exercise will
      promote improved insulin sensitivity and increased leptin in the obese. The investigators
      predict that changes in average 24-hour plasma leptin levels will correlate with
      self-selected energy intake in lean individuals, but only during overfeeding plus exercise in
      obese individuals.

      In addition, because the hunger and satiety response in humans is complex, this study will
      characterize the average 24-hour plasma levels of ghrelin, which stimulates hunger, and
      peptide YY, which stimulate satiety or fullness, in lean and obese individuals to determine
      if plasma levels are altered in obesity and in response to short-term positive energy
      balance.

      Lastly, this study involves the banking of blood tissue specimens for future research. If it
      is decided such analysis is of scientific value, genetic analysis will be conducted for
      alterations in genes involved in the synthesis of, or receptors for, hunger and satiety
      hormones to be investigated under this study design.
    

Intervention name(s): Exercise or Sedentary
Intervention type(s): Other
Intervention description(s): Daily cycling exercise at 50% maximal aerobic fitness for a total of ~120 minutes/day or no daily exercise (sedentary)
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Obesity; Appetite; Hormones; Exercise; Body Weight