Many adults do not get enough sleep as previous studies noted that over 30% of adults in several developed countries reported less than the recommended 7 hours of sleep. Insufficient sleep increases the odds of obesity and death compared to people who have adequate sleep. Changes that promote weight gain after curtailed (shortened) sleep need to be identified. Strategies that might be able to overcome weight gain-related changes resulting from insufficient sleep should also be explored. In addition to sleep duration, a person’s preferred time for activities and sleep cycle, the so-called chronotype, has been linked to certain eating behaviors which could promote weight gain. However, these relationships are poorly characterized among US adults. The overall objective of the research was to explore relationships between sleep and selected weight gain-related eating behaviors.The effects of sleep curtailment on appetite, food cravings, food reward, and portion size selection were explored in women without obesity. A total of 24 participants underwent a habitual sleep night and a curtailed sleep night, during which sleep was reduced by 33%. Participants experienced greater hunger, food cravings, and food reward after one night of curtailed sleep. Larger portion sizes were selected after curtailed sleep, which led to an increase in the amount of energy plated for lunch. These undesirable responses that followed sleep curtailment could be contributors to weight gain (chapter 2). Given that sleep curtailment led to changes in appetitive sensations and food cravings, which could lead to weight gain, it is imperative to explore possible strategies for these changes. High protein intake has been shown to provide greater satiation than other macronutrients. For this reason, chapter 3 explored the effect of a high-protein breakfast on appetitive sensations, food cravings, and dietary intake after both habitual and curtailed sleep nights. A total of 27 non-obese women underwent habitual and curtailed sleep nights followed by a high protein breakfast or a high carbohydrate breakfast. The findings demonstrated that a high protein breakfast increased fullness after participants experienced habitual sleep, but this beneficial effect disappeared after a night of curtailed sleep. Food cravings decreased after participants consumed a high protein breakfast, regardless of sleep condition. Overall, the beneficial effects of high protein breakfast mainly occurred after participants had sufficient sleep. The final chapter explored the relationships among chronotype, dietary behaviors, diet quality, and food cravings. Individuals identified as having evening-type chronotypes consumed snacks more frequently and consumed more energy-dense snacks than morning-types. However, chronotype was not related to sugar-sweetened beverage or alcohol consumption, energy and macronutrient intake, diet quality, or food cravings. The findings suggest that chronotype is negligibly related to specific behaviors associated with weight gain. In summary, the work presented revealed the effects of insufficient sleep and explored a possible strategy to address the increased appetite and food cravings after sleep curtailment in women. It also identified the relationships between chronotype and eating behaviors in adults living in the United States.
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