Restricting food intake increases the reward value of food, and the more
successful people are at caloric-restriction dieting, the greater difficulty
they will face in maintaining the restriction.
The story is a familiar one: most people are able to lose weight while
dieting but once the diet is over, the weight comes back. Many of us can
personally attest that caloric deprivation weight loss diets typically do not
produce lasting weight loss. Oregon Research Institute (ORI) senior scientist
Eric Stice, PhD, 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 more comprehensive description of the impact of
Results suggest that restricting food intake increases the reward value of
food, particularly high-calorie, appetising food (chocolate milkshakes), 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. Results imply that dieting characterised by meal skipping
and fasting would be less successful than weight loss efforts characterised by
intake of low energy dense healthy foods.
"These results are unique," said Stice "in that these data are the first to
suggest that elective caloric restriction increases the degree to which brain
regions implicated in reward valuation and attention are activated by exposure
to palatable foods."
Brain imaging paradigm
Participants were two groups of adolescents (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 a brain imaging paradigm, Stice and his team examined the responsivity
of adolescent'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. In a second paradigm, the team measured teen's neural
responses to consumption and anticipated consumption of a chocolate milkshake
and a calorie-free tasteless solution.
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
youth 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
"The implications of this imaging study are crystal clear; if people want to
lose excess weight, it would be more effective to consume healthy,
low-fat/low-sugar foods during regular meals, rather than go for long periods of
time without any caloric intake," says Dr Stice.
Funded by the National Institutes of Health (NIH), Stice has been studying
eating disorders and obesity for 20 years. He has conducted this line of
research at Stanford University and the University of Texas, and now continues
at the Oregon Research Institute in Eugene, Oregon. This line of research has
produced several prevention programmes that effectively reduce risk for onset of
eating disorders and obesity.