Posts tagged weight
Articles and news from the latest research reports.
New clues to how the brain and body communicate to regulate weight
Maintaining a healthy body weight may be difficult for many people, but it’s reassuring to know that our brains and bodies are wired to work together to do just that—in essence, to achieve a phenomenon known as energy balance, a tight matching between the number of calories consumed versus those expended. This careful balance results from a complex interchange of neurobiological crosstalk within regions of the brain’s hypothalamus, and when this “conversation” goes awry, obesity or anorexia can result.
Given the seriousness of these conditions, it’s unfortunate that little is known about the details of this complex interchange. Now research led by investigators at Beth Israel Deaconess Medical Center (BIDMC) provides new insights that help bring order to this complexity. Described in the October 26 issue of the journal Cell, the findings demonstrate how the GABA neurotransmitter selectively drives energy expenditure, and importantly, also help explain the neurocircuitry underlying the fat-burning properties of brown fat.
"Our group has built up a research program with the overall goal of unraveling the ‘wiring diagram’ by which the brain controls appetite and the burning of calories," says senior author Bradford Lowell, MD, PhD, a Professor of Medicine in BIDMC’s Division of Endocrinology and Harvard Medical School. "To advance our understanding to this level, we need to know the function of specific subsets of neurons, and in addition, the upstream neurons providing input to, and the downstream neurons receiving output from, these functionally defined neurons. Until recently, such knowledge in the hypothalamus has been largely unobtainable."
Snacking and BMI Linked to Double Effect of Brain Activity and Self-Control
ScienceDaily (July 23, 2012) — Snack consumption and BMI are linked to both brain activity and self-control, new research has found.
Snack consumption and BMI are linked to both brain activity and self-control, new research has found. (Credit: © farbkombinat / Fotolia)
The research, carried out by academics from the Universities of Exeter, Cardiff, Bristol, and Bangor, discovered that an individual’s brain ‘reward centre’ response to pictures of food predicted how much they subsequently ate. This had a greater effect on the amount they ate than their conscious feelings of hunger or how much they wanted the food,
A strong brain response was also associated with increased weight (BMI), but only in individuals reporting low levels of self-control on a questionnaire. For those reporting high levels of self-control a stronger brain response to food was actually related to a lower BMI.
This study, which is now published in the journal NeuroImage, adds to mounting evidence that overeating and increased weight are linked, in part, to a region of the brain associated with motivation and reward, called the nucleus accumbens. Responses in this brain region have been shown to predict weight gain in healthy weight and obese individuals, but only now have academics discovered that this is independent of conscious feelings of hunger, and that self-control also plays a key role.
Following these results, academics at the University of Exeter and Cardiff have begun testing ‘brain training’ techniques designed to reduce the influence of food cues on individuals who report low levels of self-control. Similar tests are being used to assist those with gambling or alcohol addiction.
Dr Natalia Lawrence of Psychology at the University of Exeter, lead researcher in both the original research and the new studies, said: “Our research suggests why some individuals are more likely to overeat and put on weight than others when confronted with frequent images of snacks and treats. Food images, such as those used in advertising, cause direct increases in activity in brain ‘reward areas’ in some individuals but not in others. If those sensitive individuals also struggle with self-control, which may be partly innate, they are more likely to be overweight. We are now developing computer programs that we hope will counteract the effects of this high sensitivity to food cues by training the brain to respond less positively to these cues.”
Twenty-five young, healthy females with BMIs ranging from 17-30 were involved in the study. Female participants were chosen because research shows females typically exhibit stronger responses to food-related cues. The hormonal changes during the menstrual cycle affect this reaction, so all participants were taking the monophasic combined oral contraceptive pill. Participants had not eaten for at least six hours to ensure they were hungry at the time of the scan and were given a bowl containing 150 g (four and a half packets) of potato chips to eat at the end of the study; they were informed that potato chip intake had been measured afterwards.
Researchers used MRI scanning to detect the participants’ brain activity while they were shown images of household objects, and food that varied in desirability and calorific content. After scanning, participants rated the food images for desirability and rated their levels of hunger and food craving. Results showed that participants’ brain responses to food (relative to objects) in the nucleus accumbens predicted how many potato chips they ate after the scan. However, participants’ own ratings of hunger and how much they liked and wanted the foods, including potato chips, were unrelated to their potato chip intake.
This study was funded by the Wales Institute of Cognitive Neuroscience.
What this study shows:
- Brain responses to food images vary considerably between individuals.
- Brain responses to food images but not conscious feelings of hunger or desire to eat predict subsequent potato chip consumption.
- Individuals’ reported levels of self-control influence whether this brain response is associated with a higher or lower BMI.
What this study does NOT show:
- Brain responses to food cues cause overeating.
- The associations reported here are true in everyone — only healthy young women were included.
- Whether our brain response and levels of self-control are learned or innate.
Source: Science Daily