Directions: Read the passage given below and answer the following questions:
Many observational and epidemiological studies have shown a connection between obesity and sleep deprivation in Americans. Alarmingly, 28% of American adults sleep less than six hours a night. One common reason for this connection is that sleep restriction affects the regulation of appetite hormones like ghrelin and leptin. Energy balance is tightly regulated by a hormonal system, involving ghrelin and leptin, which conveys information from the body to brain centers that control energy intake and expenditure. Restricted sleep is thought to increase ghrelin and decrease leptin, which promotes hunger. Sleep restriction is also thought to increase cortisol release, increasing eating behavior. Another proposed mechanism is that people, who stay awake longer, are exposed to a higher energy intake, specifically by snacking. Nevertheless, these explanations have been questioned.
The effect of neuronal activity on food stimuli, an increase in energy intake, and the effect on energy expenditure will be reviewed in relation to sleep deprivation and obesity. In one study published in The American Journal of Clinical Nutrition, researchers examined the effect on brain response to food stimuli in habitual and restricted sleep normal-weight individuals. The neuronal pattern found in the restricted sleep group was similar to one that would occur when the body is at low body weight and is trying to restore body stores. This study concluded that the restricted sleep group had a greater food intake and greater brain stimuli to areas that are linked with motivation and desire. The stimulated brain areas were the orbitofrontal cortex, insula, thalamus, precuneus, cingulate, gyrus, and supramarginal gyrus. With food being widely accessible, this could be one reason associated with weight gain during sleep restriction. However, studies have shown that there are differences between brain responses to satiety and food stimulation in obese and lean individuals. Further research needs to be conducted to see if sleep restriction affects this difference.