Too little sleep may trigger the “munchies” by raising levels of appetite-controlling molecule 2-AG

http://www.sciencedaily.com/releases/2013/06/130617110935.htm

 The researchers found that when healthy, lean, young adults received only 4.5 hours of sleep a night, they had higher daytime circulating, or blood, levels of a molecule that controls the pleasurable aspects of eating, compared with when they slept 8.5 hours.

"The mechanism for overeating after inadequate sleep may be an elevation in this endocannabinoid molecule, called 2-arachidonoylglycerol, or 2-AG.

studied nine subjects with an average age of 23 years. The subjects spent six nights in a sleep lab and then another six nights there at least a month later. In a random order, the subjects were allowed to sleep from 11 p.m. to 7:30 a.m. ("normal sleep -- 8.5 hours in bed") during one testing period and from 1 to 5:30 a.m. ("partial sleep restriction -- 4.5 hours in bed") during the other testing period. During waking hours, the subjects ate a controlled number of calories based on their height and weight.After the second night of each sleep condition, the researchers took blood samples from the subjects at one-hour intervals for 24 hours. Using a highly accurate laboratory assay, they analyzed the samples for 2-AG, a component of the endocannabinoid system. Found throughout the body, this system plays an important role in the signaling of rewarding events and one's enjoyment of eating, similar to the cannabinoids in marijuana, Hanlon said.Levels of 2-AG levels were the lowest halfway through sleep and the highest in the early afternoon, "when the pleasurable properties of food would be most beneficial," Hanlon said. She reported that the afternoon peak of 2-AG was even higher when the study participants had partial sleep restriction than when they had normal sleep.

Deep brain stimulation of the so-called “feeding centre” (the lateral hypothalamic area) was associated with weight loss via increased metabolism in morbidly obese patients

http://www.sciencedaily.com/releases/2013/06/130613092007.htm

After nine months, one patient who had experienced a 9 percent increase in resting metabolic rate reduced his weight by 16.4 percent. Another patient, whose metabolic chamber metabolic rate change was indeterminate due to motion during the selected stimulation approach, lost 12.3 percent of her weight after 11 months at the optimal setting. The final patient had a 0.9 percent decrease after 16 months at optimal settings, but also commented that this was the first time in her life that she did not have to fight constant hunger, and her binge eating score reduced from severe to within normal range.

The team believes expanded research studies might show that optimal settings would reduce appetite and food cravings, as well… In order for survival during lean times, humans have evolved to automatically lower metabolic rate when food intake goes down -- an innate "set point" that can add challenge to weight-loss efforts. This work by Oh and colleagues suggests that the "set point" can be adjusted like a thermostat.

Anorexia and bulimia correlate with altered neural circuitry

http://www.sciencedaily.com/releases/2013/06/130604093835.htm

Anorexia and bulimia correlate with altered neural circuitry

"However, this study confirms earlier studies by our group and others that establish a clear link between these disorders and neural processes in the insula, an area of the brain where taste is sensed and integrated with reward to help determine whether an individual hungry or full."

"One possibility is that restricted eating and weight loss occurs in anorexia because the brain fails to accurately recognize hunger signals," said Oberndorfer. "Alternately, overeating in bulimia could represent an exaggerated perception of hunger signals."

"It may be possible to modulate the experience by, for example, enhancing insula activity in individuals with anorexia or dampening the exaggerated or unstable response to food in those with bulimia," said Kaye. Studies indicate that healthy subjects can use real-time fMRI, biofeedback or mindfulness training to alter the brain's response to food stimuli. For patients with anorexia who have an overly active satiety signal in response to palatable foods, the researchers suggest bland or even slightly aversive foods might prevent the brain's overstimulation. Medications may also be found that enhance the reward response to food, or decrease inhibition to food consumption in the brain's reward circuitry.”