Locum Tenens (Temporary) Dentist – Gregory Cole, D.D.S.

Yes, according to a new study.

If the brain goes hungry, Twinkies look a lot better, a study led by researchers at Yale University and the University of Southern California has found.

Brain imaging scans show that when glucose levels drop, an area of the brain known to regulate emotions and impulses loses the ability to dampen desire for high-calorie food, according to the study published online September 19 in The Journal of Clinical Investigation.

“Our prefrontal cortex is a sucker for glucose,” said Rajita Sinha, the Foundations Fund Professor of Psychiatry, and professor in the Department of Neurobiology and the Yale Child Study Center, one of the senior authors of the research.

The Yale team manipulated glucose levels intravenously and monitored changes in blood sugar levels while subjects were shown pictures of high-calorie food, low-calorie food and non-food as they underwent fMRI scans.

When glucose levels drop, an area of the brain called the hypothalamus senses the change. Other regions called the insula and striatum associated with reward are activated, inducing a desire to eat, the study found. The most pronounced reaction to reduced glucose levels was seen in the prefrontal cortex. When glucose is lowered, the prefrontal cortex seemed to lose its ability to put the brakes upon increasingly urgent signals to eat generated in the striatum. This weakened response was particularly striking in the obese when shown high-calorie foods.

“This response was quite specific and more dramatic in the presence of high-calorie foods,” Sinha said.

“Our results suggest that obese individuals may have a limited ability to inhibit the impulsive drive to eat, especially when glucose levels drop below normal,” commented Kathleen Page, assistant professor of medicine at the University of Southern California and one of the lead authors of the paper.

A similarly robust response to high-calorie food was also seen in the striatum, which became hyperactive when glucose was reduced. However, the levels of the stress hormone cortisol seemed to play a more significant role than glucose in activating the brain’s reward centers, note the researchers. Sinha suggests that the stress associated with glucose drops may play a key role in activating the striatum.

“The key seems to be eating healthy foods that maintain glucose levels,” Sinha said. “The brain needs its food.”

The abstract for the paper:

Obesity is a worldwide epidemic resulting in part from the ubiquity of high-calorie foods and food images. Whether obese and nonobese individuals regulate their desire to consume high-calorie foods differently is not clear. We set out to investigate the hypothesis that circulating levels of glucose, the primary fuel source for the brain, influence brain regions that regulate the motivation to consume high-calorie foods. Using functional MRI (fMRI) combined with a stepped hyperinsulinemic euglycemic-hypoglycemic clamp and behavioral measures of interest in food, we have shown here that mild hypoglycemia preferentially activates limbic-striatal brain regions in response to food cues to produce a greater desire for high-calorie foods. In contrast, euglycemia preferentially activated the medial prefrontal cortex and resulted in less interest in food stimuli. Indeed, higher circulating glucose levels predicted greater medial prefrontal cortex activation, and this response was absent in obese subjects. These findings demonstrate that circulating glucose modulates neural stimulatory and inhibitory control over food motivation and suggest that this glucose-linked restraining influence is lost in obesity. Strategies that temper postprandial reductions in glucose levels might reduce the risk of overeating, particularly in environments inundated with visual cues of high-calorie foods.

It is common knowledge in running endurance training (e.g. marathon training) that you need to maintain blood glucose levels in order to avoid “negative thoughts” from the brain. Thoughts that will persuade you to stop running.

So, why should this be any different throughout the day or evening when we are not stressing our bodies?

Interesting how obesity plays a role, where an obese person sort of loses their way with regulating their desires for high calorie food.

The entire paper is here. The PDF file is here

This post of a paper caught my eye this morning, since I am dieting and trying to reduce my body weight. I am using My Fitness Pal online and count calories in and exercise calories expended. So far I have lost about 9 pounds.

Common rules of thumb exaggerate how much weight people will lose from a given dietary calorie reduction, leading to unrealistic expectations and disappointment, researchers said.

Whereas patients are often told that cutting 500 calories a day will let them lose a pound a week, a more realistic formula is that such a caloric reduction would lead to a 50-pound loss over three or more years, according to Kevin D. Hall, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., and colleagues.

Even then, they explained in the Aug. 27 issue of The Lancet — a special edition devoted to obesity — such weight loss is possible only if the calorie reduction is actually maintained over that time.

The standard rules — endorsed by the National Institutes of Health and the American Dietetic Association, among others — fail to consider that human metabolism responds dynamically to changes in diet and body composition, Hall and colleagues asserted.

If a 300-pound dieter could really lose a pound a week by cutting his regular diet by 500 calories, he would vanish entirely in six years.

“This ubiquitous weight-loss rule (also known as the 3,500 [calorie]-per-pound rule) was derived by estimation of the energy content of weight lost, but it ignores dynamic physiological adaptations to altered body weight that lead to changes of both the resting metabolic rate as well as the energy cost of physical activity,” the researchers wrote.

When people gain weight, their baseline energy needs increase, to keep the extra tissue alive and to move it around. Likewise, when weight is lost, their baseline needs decrease.

So when people cut calories below the baseline requirement — thereby triggering weight loss — the gap between their intake and their baseline energy needs begins to shrink. At some point, it may disappear altogether, at which point weight loss stops.

Hall and colleagues put together what they said was a better model of caloric intake and resultant weight loss, incorporating feedback mechanisms to reflect metabolic changes over time in response to diet and body weight.

It indicated that weight change in response to caloric restriction occurs over a relatively long period of time.

Each reduction of 100 kilojoules daily — 24 calories — in intake eventually leads to a loss of 1 kg (2.2 lbs) in body weight, the researchers determined. But only half that loss occurs in the first year. In three years, 95% of the ultimate loss will be realized.

On the flip side, using data from previous studies, Hall and colleagues said their calculations suggest that the U.S. population has a persistent excess energy intake of 30 kilojoules (7.2 calories) per day, explaining the increasing prevalence of overweight and obesity.

For the population to return to body mass index values that prevailed in the 1970s, average diets would need to shrink by about 220 calories per day.

The researchers pointed out that these figures are averages for the adult population. Individuals’ metabolic requirements for sustaining a given body mass vary substantially.

Consequently, “a given diet results in an uncertain degree of energy deficit,” Hall and colleagues wrote.

I suppose I will just have to be patient and wait the three to five years to reach my weight goal. But, then again, I have been packing on the extra weight for decades now and I cannot expect a quick fix.

I can do it.