HPC-UK Bitesize (Fat Loss): Dieters Show Greater Brain Reward Activity in Response to Food

Despite the huge knowledge explosion we have had in the physiology world in the last decade, especially since the human genome project produced the genomic map, the mainstream ‘weight loss’ industry still haven’t really changed their mantra of ‘Eat less’. I’ve shown previously multiple ways why this doesn’t work as advertised, in terms of actual fat lost (there is some temporary loss of the fat droplet inside the fat cell, but plenty of muscle and unfortunately for women bone loss too), nor does it cause a permanent change to your physiology, especially the functioning of the fat cell itself, so that you are able to maintain a lower fat body. Even if it did work, a recent study has shown one of the mechanisms that makes it difficult to achieve long term.

Oregon Research Institute (ORI) senior scientist Eric Stice, Ph.D., and colleagues provide results in a recent issue of NeuroImage that further our understanding of how and why most weight loss diets fail and provide a description of the impact of caloric restriction.

The study suggests that restricting food intake increases the reward value of food, particularly high-calorie, appetizing food, and that the more successful people are at caloric-restriction dieting, the greater difficulty they will face in maintaining the restriction. Additionally, abstaining from food intake for longer durations of time also increases the reward value of food, which may lead to poor food choices when the individual eventually does eat.

The data suggests that elective caloric restriction increases the degree to which brain regions implicated in reward valuation and attention are activated by exposure to palatable foods.

Participants in the study were split into two groups (Study 1 n=34; Study 2 n=51) who voluntarily restricted their caloric intake so as to approximate what occurs with real-world dieters. Using brain imaging the research team examined the responsivity of the subject’s attention and reward regions of the brain to the individual's exposure to and imagined intake of palatable foods, unpalatable foods, and glasses of water shown in pictures. By including both pictures of palatable and unpalatable foods, the team was able to determine whether degree of "self-imposed" caloric deprivation correlated with hyper-responsivity of attention and reward regions for palatable versus unpalatable foods.

The team also measured the subject’s neural responses to consumption and anticipated consumption of a chocolate milkshake and a calorie-free tasteless solution. The lead researcher Dr. Stice examined whether the number of hours since last caloric intake (which varied from 3 to 22 hours) correlated with neural activation in response to receipt and anticipated receipt of a palatable food. They also tested whether the subject’s who were in a negative energy balance for a 2-week period versus energy balance or a positive energy balance showed aberrant neural response to food stimuli.

The research team concluded that the implications of this imaging study suggest that if people want to lose excess weight, it would be more effective to consume healthy, lower energy dense foods during regular meals, rather than go for long periods of time without any caloric intake.

Reference:

Eric Stice, Kyle Burger, Sonja Yokum. Caloric deprivation increases responsivity of attention and reward brain regions to intake, anticipated intake, and images of palatable foods. NeuroImage, 2013; 67: 322 DOI: 10.1016/j.neuroimage.2012.11.028