Dieting youth show greater brain reward activity in response to food, says a new study on small portions. 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, 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 more comprehensive description of the impact of caloric restriction.
Results suggest that restricting food intake increases the reward value of food, particularly high-calorie, appetizing 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 characterized by meal skipping and fasting would be less successful than weight loss efforts characterized by intake of low energy dense healthy foods.
Elective caloric restriction increases the degree to which specific brain regions are activated by exposure to palatable foods
“These results are unique, 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,” explains Eric Stice, in the May 2, 2013 news release, “Dieting youth show greater brain reward activity in response to food.” Those specific brain regions are related to getting the rewards of attention and valuation through being exposed to tasty foods.
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.
Self-imposed food deprivation: What are the results?
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 stimuli.
Consuming low-fat, low-sugar foods during regular meals are better for the health than fasting for long periods
“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 programs that effectively reduce risk for onset of eating disorders and obesity.
The research described here is funded in part by the National Institute of Diabetes and Digestive and Kidney Diseases of the NIH under grants R01DK072932 and R01DK092468, and in part by the National Institute of Mental Health of the National Institutes of Health (NIH) grant R01MH64560. The content is the sole responsibility of the authors and does not necessarily represent the official views or imply endorsement of the NIH. Oregon Research Institute is a non-profit, independent behavioral research center with headquarters in Eugene. Founded in 1960, it also has offices in Portland, Oregon and Albuquerque, New Mexico.
Why kids watching their weight-gain issues shouldn’t be eating after 7:00 p.m.
Children eating after dark and during the night hours may gain more weight than if the kitchen closed before 7:00 p.m. and snacks were not served in the evening after an early dinner except for water. Did you know your body’s inner clock may regulate weight gain?
How many people eat in those 24-hour fast food restaurants and then wonder why they seem to be putting on more weight after eating late in the evening or at night? You’ll notice in most urban areas a whole string of eateries with the open 24 hours sign outside featuring food fried in high heat and served to a night life crowd that enjoys eating after theater, after the cinema, after the night clubs close, or simply after usual eating hours.
You also have nurses and doctors working all night who eat at unusual times because they are working the night shift at hospitals. And then there’s the police eating at night when they can take a food break, and all the workers who are on the night shift or swing shift at various types of industries. Are they all experiencing some gain in weight after starting to eat late at night because of their working hours?
Children often get up from sleep hungry to snack after everyone’s gone to bed
Some people even get up from sleep hungry and go to the refrigerator for a snack after midnight, perhaps because they haven’t eaten foods during the day that feel filling enough to get through the night. Others eat too much at night when their main meal of the day should be at noon or even at breakfast.
You’ll have a greatly increased risk of weight gain if you eat at night. This would include getting up late at night to eat a snack. You gain more weight when you eat at the wrong time of day for your specific metabolism. See the research article in the journal, Obesity, “Circadian Timing of Food Intake Contributes to Weight Gain.”
For more information on how biorhythms affect the individual human body in different ways, see my other Examiner article for more detailed information on biological clocks: “How biorhythms and food balance your inner clocks.”
Wise food and chronobiology traditions reveal that what is certain is that the person you are in the morning is different from the one you are at night. Your blood pressure rises between 8 a.m. and 12 noon, then starts dropping until it’s midnight low. There’s an internal clock governing your hormone levels and your heartbeat, all following different clocks that may bear only a slight relation to your daily cycle.
Individuals respond to this regulation by periodic changes in their growth and behavior patterns. Jet lag is one example of what happens when the internal clock is out of whack.
Morning people have a higher body temperature than the afternoon or evening person. That’s what gives them that early morning burst of energy.
All these inner clocks, your biorhythms, are affected by whether you start the day with specific types of protein or complex carbohydrates. And if you’re eating whole grains, for energy, it’s part of wise food traditions to let the whole grains ferment overnight in a refrigerated jar or pot of filtered water.
Research has been done at Chicago’s Northwestern University and at Weinberg College of Arts and Science’s Center for Sleep and Circadian Biology. How the weight gain occurs is that your body is regulated by biorhythms, also called circadian rhythms. When those rhythms are interrupted, weight gain could occur.
The regulation mechanism for the circadian rhythms is being researched to see what role it plays in weight gain from eating during hours your body normally would be sleeping. The research results would be applied to the study of excess weight loss strategies based on timing meals according to your individual chronobiology or circadian rhythms.
Research on the effects of eating at night on increased weight gain comes under the category of studies in neurobiology and physiology. In the original experiments, mice were fed a high fat diet during the time the mice would normally be asleep.
On the other hand, the research on mice may or may not be applicable to humans. So the studies remain inconclusive until science shows humans react the same way.
Don’t eat at night: Let 16 hours pass after dinner until breakfast the next morning
Naturopaths, on the other hand, have long warned people not to eat at night. Some nutritionists suggest people not eat after 4:00 pm if they are older and lack enough digestive enzymes, which could result in acid reflux when lying flat.
Other nutritionists recommend taking a teaspoon of apple cider vinegar to make up for the lack of digestive enzymes in older adults. In the eating at night experiments with mice, what the scientists were trying to determing is how biorhythms, chronobiology, and circadian inner clocks influence eating habilts.
Results have been published in the medical journal, Obesity. The journal, Obesity, also has an informative article, “High glycemic index diet quickly lowers plasma antioxidant levels.” For more information on how circadian clocks affect the human body, you can read the article, Chronobiological Interventions in Mood Disorders.
Pay attention to your molecular clock
The research noted in the article, Chronobiological Interventions in Mood Disorders stated that “studies provide evidence that chronobiological treatments (SPA/TSD/light therapy) may represent novel and safe augmentation strategies that could contribute to the management of unipolar and bipolar depression.”
There is also preliminary evidence suggesting that variations in genes supporting the molecular clock (CLOCK and GSK3-b) may influence core features of bipolar disorder, such as age at onset and rate of recurrence. See the article, Serretti A, Benedetti F, Mandelli L, et al. “Genetic dissection of psychopathological symptoms: insomnia in mood disorders and clock gene polymorphism.” Am J Med Genet. 2003;121B