National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
The NIDDK Recent Advances & Emerging Opportunities is a compendium that highlights examples of the many research advances published by NIDDK-funded scientists and their colleagues in the most recent fiscal year, along with the technologies that made these achievements possible. This compendium also includes a section devoted to recent advances in obesity research at NIDDK.
This section provides examples of recent scientific advances from NIH-sponsored research, and is not intended to be a comprehensive list.
Researchers found that sleep restriction alters levels of endocannabinoids—chemical signals that affect appetite and the brain's reward system. The researchers enrolled 14 healthy, non-obese men and women. The participants were allowed either a normal 8.5 hours of sleep or a restricted 4.5 hours of sleep for 4 consecutive days. All participants were subjected to both sleep conditions with at least 4 weeks in between testing. When sleep-deprived, participants' endocannabinoid (eCB) levels were both higher and lasted longer than when they'd had a full night's rest. The eCB increase occurred around the same time that they reported increases in hunger and appetite. When sleep-deprived, participants consumed more and unhealthier snacks in between meals. This is when eCB levels were at their highest, suggesting that eCBs were driving hedonic, or pleasurable, eating. The results may help explain the link between insufficient sleep and obesity.
People with obesity who reduced their weight by 5% had improvements in metabolic function in many tissues, including fat, liver, and muscle, according to an NIDDK-funded study. The scientists randomly assigned 40 sedentary people with obesity to maintain their weight or to go on a diet to lose 5% of their body weight, followed by targets of 10% and 15%. Nineteen participants who achieved 5% weight loss had significantly decreased body fat and plasma levels of glucose, insulin, triglycerides, and leptin, which are risk factors for heart disease and diabetes. They also showed improved function of insulin-secreting β cells, as well as the ability of fat, liver, and muscle tissue to respond to insulin. Further weight loss of 10 to 15% resulted in some additional improvements. "Our findings demonstrate that you get the biggest bang for your buck with 5% weight loss," said the study lead, Dr. Samuel Klein of Washington University School of Medicine in St. Louis.
A single variation in the gene coding for brain-derived neurotropic factor (BDNF) may influence obesity in children and adults, according to a new NIH-funded study. The researchers studied the variance in the sequence of the BDNF gene in more than 31,000 males and females enrolled in clinical research studies. The BDNF protein plays several roles in the brain and nervous system and, at high levels, can stimulate the feeling of fullness. Researchers compared subjects' individual BDNF gene versions to factors that define obesity, such as body mass index (BMI) and percentage of body fat. They found that one particular version of the gene—the "C" allele—was associated with higher BMI and percentage of body fat. In laboratory experiments, a protein involved in the regulation of the BDNF gene expression had trouble interacting with the C allele, resulting in less BDNF protein produced. "Lower BDNF levels may contribute to obesity in people with the C allele. Boosting BDNF levels may prove beneficial," said the study lead, Joan Han, M.D. of the University of Tennessee Health Science Center.
In adults with obesity, decreasing dietary fat led to greater body fat loss than cutting the same number of calories from carbohydrates. A research team led by Dr. Kevin Hall of NIDDK enrolled 10 men and 9 women with obesity. The participants stayed in the metabolic clinical research unit on the NIH campus for 2 visits of about 2 weeks each. For the first 5 days of each stay, the volunteers were given a balanced diet (50% carbohydrate, 35% fat, and 15% protein). Over the next 6 days, they received a diet with 30% fewer calories. On one visit, the calorie decrease came solely by cutting carbohydrates. On the other visit, the calories were cut only from dietary fat. Compared to the reduced-fat diet, the reduced-carb diet was particularly effective at lowering insulin secretion and increasing fat burning, resulting in significant body fat loss. But interestingly, study participants lost even more body fat during the fat-restricted diet, possibly because fat-restricted diet led to a greater imbalance between the fat eaten and fat burned. The study findings show that, contrary to popular belief, carbohydrate restriction is not needed for body fat loss.
For the first time in a lab, researchers found evidence supporting the commonly held belief that people with certain physiologies lose less weight than others when limiting calories. They studied 12 men and women with obesity in the NIDDK Phoenix Epidemiology and Clinical Research Branch metabolic unit. Using a whole-room indirect calorimeter—which allows energy expenditure to be calculated based on air samples—researchers took baseline measurements of the participants’ energy expenditure in response to a day of fasting, followed by a six-week inpatient phase of 50% calorie reduction. They found that the people who lost the least weight during the calorie-reduced period were those whose metabolism decreased the most during fasting. Those people have what the researchers call a “thrifty” metabolism, compared to a “spendthrift” metabolism in those who lost the most weight and whose metabolism decreased the least. The results corroborate the idea that some people who are obese may have to work harder to lose weight due to metabolic differences. These findings may one day enable a more personalized approach to help people who are obese achieve a healthy weight.
It's normal for most women to gain weight during pregnancy, but gaining too much weight can pose serious health risks for both mother and baby. These risks are greater for women who are already obese when they become pregnant. Researchers helped obese women limit their weight gain during pregnancy by asking them to follow a healthy diet based on the Dietary Approaches to Stop Hypertension (DASH) eating pattern, which is high in fruits and vegetables and includes lean meats, lean proteins like chicken, fish, and low-fat beef, as well as whole grains. Participants were also asked to reduce their consumption of sweets and sweetened drinks and to track their dietary intake by keeping daily food records. Women in this intervention group gained significantly less weight than women in the control group, who received no advice or weight monitoring. The intervention group was also less likely to have large-for-gestational-age babies (those bigger than 90 percent of the babies of the same gestational age and gender), who are at increased risk for various health conditions. According to the study's lead author, Dr. Kim Vesco of the Kaiser Permanente Center for Health Research in Portland, Oregon, an important next step would be to work within the health care system to implement these beneficial strategies.
Overweight and obese adults who drink diet beverages consume significantly more solid-food calories—particularly from snacks—than those who drink sugary beverages. The findings highlight the challenges in using diet beverages to help control weight. Diet beverage use has skyrocketed in recent decades. It's now a common weight control strategy. It might make sense to think that diet beverages would help you lose weight due to their lack of calories. But the body's mechanisms for maintaining weight are subtle and complex. Studies into how diet beverages affect weight control have found conflicting results. "The results of our study suggest that overweight and obese adults looking to lose or maintain their weight—who have already made the switch from sugary to diet beverages—may need to look carefully at other components of their solid-food diet, particularly sweet snacks, to potentially identify areas for modification," says the lead researcher on the study, Sara N. Bleich, Ph.D.