To investigate the effects of a high-fat diet on sleep, researchers put rats on a fatty-food diet for 8 weeks. The rats, no surprise, gained weight. They then monitored the rats’ 24-hour sleep-wake cycles and found that the animals’ sleep cycles had changed for the worse:
- Rats who ate the high-fat diet for 8 weeks slept more than rats on a regular diet
- These same rats also showed more fragmented sleep
- The extra sleep accrued by the high-fat-diet rats mostly occurred during the daytime.
Orexin (also known as hypocretin) is a neuro-chemical that plays a critical part in regulating our daily sleep-wake cycle as well as in managing appetite.
- Orexin is one of several chemicals in the brain that help govern our 24-hour sleep/wake cycle. In particular, orexin is involved in stimulating wakefulness. A lack of orexin can lead to serious disruptions to daily life: orexin deficiency is believed to be a primary cause of the sleep disorder narcolepsy. People with narcolepsy experience extreme levels of daytime sleepiness and “sleep attacks,” when they may fall asleep abruptly at any time during the day.
- Orexin is active in the hypothalamus region of the brain. Known as the “feeding center,” the hypothalamus is the part of the brain involved in regulating appetite, hunger, and impulse control. Orexin has been shown in studies to be directly involved in the complicated chemical process that creates the urge to eat.
- Researchers who examined mice genetically engineered with orexin deficiency found that these mice were heavier than normal mice, despite being fed a more restrictive diet. Researchers discovered that the mice bred to lack orexin had not developed a special type of fat -- brown fat -- that actually functions as a fat-burning engine in the body.
- In one study, rats were fed a high-fat diet and gained weight. These rats demonstrated a significant drop in activity levels compared to their levels of physical activity before they started the diet. These rats also showed a decrease in their sensitivity to orexin.