If you find yourself famished after you've managed to diet away a sizable number of pounds, you're not alone.
Cutting back on calorie consumption is likely to spark changes that permanently boost appetite among obese men and women, Norwegian researchers report.
Blame it on the hunger hormone ghrelin, which spikes when you suddenly lower your food intake. It's a phenomenon that harkens back to when early humans had to survive bouts of famine, the researchers said.
Now, that ancestral hormonal swing may undermine long-term efforts to keep the weight off, judging by what happened to 35 morbidly obese patients as they spent two years on a highly structured weight-loss program.
"It is extremely important that both patients with obesity and health professionals working with them are aware of the expected increase in hunger with weight loss," said study author Catia Martins. "This can explain why it is so difficult, at least for some individuals with obesity, to comply with energy-restricted diets, and why so many give up."
Martins is an associate professor with the faculty of medicine at the Norwegian University of Science and Technology.
The statistics can be disheartening: The researchers noted that only 1 in 5 obese dieters is able to keep off the weight he or she sheds.
The study focused on 22 women and 13 men in Norway who were about 275 pounds, on average, and characterized as "severely obese," before embarking on a highly supportive weight-loss program.
First, all underwent a three-week inpatient program that offered nutritional education, psychological counseling and routine exercise activities. Four more three-week sessions were completed over the course of the program.
Throughout, all participants were placed on a "moderately restricted" diet. This meant consuming about 500 calories per day less than otherwise needed to maintain a status quo weight. Food breakdown was set at 50 percent carbs, 30 percent fat and 20 percent protein.
On average, the patients lost about 11 pounds within the first three weeks of the program, and an average of 24 pounds by the two-year mark.
But at both the one and two-year marks all the patients also reported feeling increasing hunger following their weight loss.
Why? On the one hand, as weight went down, ghrelin levels went up and stayed up. On the other, as the participants' weight dropped their energy needs for basic functions -- such as breathing, sleeping, walking and eating -- also dropped.
And the result is strong pressure towards regaining lost weight over time, turning weight loss maintenance into a lifelong daily struggle, the researchers said.
The findings were published recently in the American Journal of Physiology-Endocrinology and Metabolism.
Lona Sandon is program director of the department of clinical nutrition with the School of Health Professions at the University of Texas Southwestern Medical Center at Dallas. The study "supports what is already known," she said.
"And the authors make a great point in regards to obesity treatment/management," said Sandon, who wasn't involved with the study. "People need long-term support, and the standard care or payment methods [health insurance] for obesity management are short-term, despite the oodles of evidence for long-term support and support beyond the physician setting."
Insurance, for example, rarely kicks in to cover the services of a registered dietitian or personal trainer, Sandon noted.
But for those anxious to minimize the hunger hormone trap, Sandon says slow and steady weight loss is the way to go.
"It may take months, six or more, of consistent daily exercise combined with mild calorie restriction, decreasing 200 to 300 calories per day, to reach a lower [hormonal] 'set point,' " she said.
But, "the slower the weight loss, and the more modest the calorie restriction to obtain weight loss, the more likely someone might keep the lost weight off," she said.
An hour a day of exercise can also help to lower a set point, Sandon added, whether that be time spent on a treadmill or time spent doing "something you enjoyed doing as a kid," like dancing, playing basketball or soccer, swimming or even roller-skating.
There's more on the importance of achieving a healthy weight at the U.S. National Heart, Lung, and Blood Institute.
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