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dimanche 8 juin 2014

Obesity Gene May Explain Why Some Gain Weight as They Age

By Dennis Thompson
HealthDay ReporterLatest Diet & Weight Management NewsIs Breakfast the Key to Weight Control?Health Tip: If You Aren't Hungry, Don't EatDiabetes Drug Spurs Weight Loss in NondiabeticsObesity Crisis Has Scaled Even the HimalayasObesity, Overweight Rates Jump Worldwide, ReportWant More News? Sign Up for MedicineNet Newsletters!

TUESDAY, May 27, 2014 (HealthDay News) -- A defective gene linked to obesity appears to affect impulse control and food choices. And this could explain why people with the gene have so much trouble maintaining a healthy weight as they age, a new U.S. study says.

Middle-aged and older people with obesity-associated variants of the FTO gene tend to gain weight, according to researchers from the National Institutes of Health. Moreover, scans detected reduced function in brain regions that govern impulsivity and perception of food texture and taste, the researchers found.

"Sure enough, people who carry one or two copies of the FTO variant show increased intake of high-calorie or fatty food as they age," said senior author Dr. Madhav Thambisetty, chief of clinical and translational neuroscience at the National Institute on Aging's Laboratory of Behavioral Neuroscience.

"There may be a common biological factor underlying both the risk for obesity during aging as well as obesity-related behavior like your ability to resist impulse eating," Thambisetty said.

Many studies have tied certain versions of the FTO gene to chronic obesity, but doctors have struggled to determine why the gene affects a person's risk of obesity, said Ruth Loos, director of the genetics of obesity and related metabolic traits program at the Icahn School of Medicine at Mount Sinai in New York City.

"These types of studies are important to disentangle the mechanism of why FTO is associated with obesity, but it's only one piece of a huge puzzle," Loos said.

In the United States, more than one-third of adults aged 65and over are obese, according to background information in the study.

About 45 percent of people in this study had at least one copy of the pro-obesity FTO variant, Thambisetty said, which tracks with the white population in the United States. About 16 percent of people had two copies of the gene, which confers an even greater risk of obesity.

The study focused on nearly 700 participants, including 69 people who agreed to annual PET scans to gather additional information regarding their brain structure and function. At the start of the study, average age was 46. All were participating in the Baltimore Longitudinal Study of Aging, one of the longest running studies of human aging in North America.

They first confirmed that body mass index increased in those with one or two copies of the FTO gene variant. They then compared brain PET scans of patients with the FTO variant with scans of non-carriers, looking for differences in brain function over time.

They found people with the gene variant had reduced function in their medial prefrontal cortex, a region thought to be important in controlling impulses and response to the taste and texture of food.

In a final step, the team reviewed data gathered on participants' personality and diet. The group at increased genetic risk for obesity showed a greater tendency to impulsivity as well as a greater intake of fatty foods during aging.

The effect appears to increase with the number of copies. "We see a dose effect, where these changes in impulsivity or a preference for fatty foods increase with multiple copies of the gene," Thambisetty said.

The findings are published May 27 in the journal Molecular Psychiatry.

If these results pan out in additional studies, they mean that people who have a greater genetic risk of obesity face an uphill battle to maintain a healthy weight.

"This should not be an excuse, but it has to be a partial explanation why intelligent and motivated individuals struggle so much, because they are fighting their biology and it's uncomfortable to fight your own biology," said Dr. Steven Lamm, medical director of the Tisch Center for Men's Health at NYU Langone Medical Center in New York City.

However, a genetic predisposition to obesity does not mean one is doomed to obesity.

"You may be genetically susceptible, but by living a healthy lifestyle you can overcome your genetics," Loos said. "You are not destined to be obese."

Thambisetty agreed, noting that previous studies have shown that people can overcome the obesity risk posed by the FTO gene through regular exercise.

Fast Weight Loss May Mean Muscle Loss

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THURSDAY, May 29, 2014 (HealthDay News) -- If you lose weight too fast, you lose more muscle than when you shed excess pounds more slowly, a small study says.

The researchers put 25 participants on a five-week very-low-calorie diet of just 500 calories per day. Another 22 volunteers went on a 12-week low-calorie diet of 1,250 calories per day.

The investigators found that right after the end of their diets, both groups had similar levels of weight loss. The average weight loss was a little over 19 pounds among those on the very-low-calorie diet and just under 19 pounds among those on the low-calorie diet.

The researchers then looked at the loss of fat-free mass, which includes all the tissue in the human body, except fat. The major tissues are blood, bones, organs and muscles. However, the mass of the organs, blood and bones does not change during dieting. Therefore, changes in fat-free mass during dieting are mainly due to changes in muscle mass.

Participants on the very-low-calorie diet had lost about 3.5 pounds of fat-free mass, compared with 1.3 pounds among those on the low-calorie diet. Fat-free mass accounted for 18 percent of weight loss in the very-low-calorie diet group and 7.7 percent of weight loss in the low-calorie diet group, the study found.

Four weeks after the end of their diets, reductions in fat-free mass averaged 1.8 pounds among those in the very-low-calorie diet group and 0.7 pounds among those in the low-calorie diet group. Fat-free mass accounted for 9.4 percent of weight loss in the very-low-calorie diet group and 2.9 percent of weight loss in the low-calorie diet group, according to the report.

The findings were presented Wednesday at the European Congress on Obesity in Bulgaria.

"Loss of fat-free mass was higher after rapid than slow diet-induced weight loss with similar total weight loss," said the study's authors, Roel Vink and Marleen van Baak, of the School for Nutrition, Toxicology and Metabolism at Maastricht University in the Netherlands, and colleagues.

However, the authors also pointed out in a meeting news release that muscle loss among people in the very-low-calorie diet was likely overestimated immediately after they completed the diet, compared with four weeks later.

This is likely because they had a larger loss of water and glycogen (a natural form of sugar in the body) when they had just completed the diet than four weeks later, the researchers explained.

Research presented at meetings should be viewed as preliminary until it is published in a peer-reviewed medical journal.

-- Robert Preidt

Obesity, Overweight Rates Jump Worldwide, Report Finds

WEDNESDAY, May 28, 2014 (HealthDay News) -- In the past three decades, the number of overweight and obese people worldwide has jumped from 857 million to 2.1 billion, a new analysis shows.

Not only that, the United States is home to the highest proportion of the world's obese people, at 13 percent.

The study shows that obesity is a major public health epidemic in both developing and developed nations, said the researchers at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington in Seattle.

They analyzed data collected between 1980 and 2013 about children and adults in 188 countries.

Rates of overweight and obesity rose from 29 percent to 37 percent among men and from 30 percent to 38 percent among women. Rates of overweight and obesity among men were higher in developed nations, while rates among women were higher in developing nations.

The researchers also found that peak obesity rates are occurring at younger ages in developed nations, according to the study that appears May 29 in The Lancet.

Rates of overweight and obese children worldwide rose by nearly 50 percent between 1980 and 2013. In 2013, more than 22 percent of girls and nearly 24 percent of boys in developed nations were overweight or obese. The rates in developing nations were nearly 13 percent for both boys and girls.

"The rise in obesity among children is especially troubling in so many low- and middle-income countries," study author Marie Ng, an assistant professor of global health at IHME, said in an institute news release.

"We know that there are severe downstream health effects from childhood obesity, including cardiovascular disease, diabetes and many cancers. We need to be thinking now about how to turn this trend around," she said.

The study also found that more than 50 percent of the world's 671 million obese people live in 10 countries: the United States, China, Russia, Brazil, Mexico, Egypt, Germany, Pakistan and Indonesia.

"Obesity is an issue affecting people of all ages and incomes, everywhere," IHME Director Dr. Christopher Murray said in the news release. "In the last three decades, not one country has achieved success in reducing obesity rates, and we expect obesity to rise steadily as incomes rise in low- and middle-income countries in particular, unless urgent steps are taken to address this public health crisis."

-- Robert Preidt

Obesity Crisis Has Scaled Even the Himalayas

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WEDNESDAY, May 28, 2014 (HealthDay News) -- Obesity rates in remote Himalayan mountain villages are five times higher than they were two decades ago, according to a new study that highlights the extent of the global obesity epidemic.

Obesity-related health issues have skyrocketed as well, the study found.

Researchers looked at data from more than 4,600 adults in the Gilgit Baltistan region of Pakistan who took part in surveys conducted in 1995 and 2013. Over those 18 years, the obesity rate rose from about 2 percent to almost 13 percent, and the proportion of overweight people increased from almost 12 percent to about 27 percent.

"Overweight and obesity is a rapidly growing public health burden in the rural population of Pakistan. Overall obesity and central obesity were significant correlates for type 2 diabetes and pre-diabetes in the high mountain study population," said Syed Shah, an associate professor at the Institute of Public Health of United Arab Emirates University, and colleagues.

The study was scheduled for presentation Tuesday at the European Congress on Obesity in Bulgaria. Findings presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.

Of the nearly 1,100 people who took part in the 2013 survey, more than 6 percent had type 2 diabetes and almost 8 percent had pre-diabetes. Those with a waist circumference of 35 inches or more were four times more likely to have diabetes than those with smaller waists. Obese people were 16 times more likely to have pre-diabetes than normal weight people.

However, the investigators also found that 9 percent of people were underweight, which shows that the region faces "a dual war" against both malnutrition and obesity, the researchers said in a European Congress news release.

-- Robert Preidt

Diabetes Drug May Spur Weight Loss in Obese Nondiabetics

By Steven Reinberg
HealthDay ReporterLatest Diet & Weight Management NewsIs Breakfast the Key to Weight Control?Health Tip: If You Aren't Hungry, Don't EatDiabetes Drug Spurs Weight Loss in NondiabeticsObesity Crisis Has Scaled Even the HimalayasObesity, Overweight Rates Jump Worldwide, ReportWant More News? Sign Up for MedicineNet Newsletters!

THURSDAY, May 29, 2014 (HealthDay News) -- The diabetes drug liraglutide (Victoza) may help obese people without the disease lose weight, a new study suggests.

In this test of its effectiveness as a diet aid, people taking Victoza for over a year lost an average of 8 percent of their body weight, compared with 2.6 percent shed by those taking a placebo (dummy drug), researchers found.

"Liraglutide, an injection treatment already approved for diabetes treatment, can help reduce body weight in people with obesity when used at a higher dose than is usually used in diabetes," said lead researcher Dr. John Wilding, head of the department of obesity and endocrinology at the University of Liverpool in England.

"These results suggest liraglutide is effective and overall well-tolerated for obesity treatment," he said.

Although this study didn't compare Victoza with other weight loss drugs, Wilding said that a previous study showed Victoza could produce about twice as much weight loss as another drug, orlistat (Xenical).

Xenical works by reducing the amount of fat the intestines can absorb. People taking Xenical lose an average of five to seven pounds, studies have shown.

Victoza works by lowering blood sugar.

The results of the study were scheduled for presentation Thursday at the European Congress on Obesity in Sofia, Bulgaria. Data and conclusions presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.

Dr. David Katz, director of the Yale University Prevention Research Center in New Haven, Conn., wasn't surprised by the findings. "A number of drugs used to treat type 2 diabetes tend to produce weight loss as one of their effects," said Katz, who was not involved in the study.

This is predictable because the insulin resistance that precedes and often accompanies type 2 diabetes results in frequent hunger and weight gain. Lowering blood sugar results in weight loss, he said.

Whether Victoza improves long-term weight management or leads to better health outcomes over years when used for weight loss is unknown, he said.

"But for now, Victoza takes its place alongside other drugs studied initially for diabetes, but

Health Tip: If You Aren't Hungry, Don't Eat

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(HealthDay News) -- People often eat, not out of hunger, but because they're bored and seem to have nothing better to do.

The American Heart Association suggests how to avoid eating for reasons other than hunger:

Make sure you eat three meals per day. You may wind up eating more at mealtime if you skipped an earlier meal.If you binge eat a specific food (such as ice cream, candy or chips) don't keep that food at home.Create a list of things to do in lieu of eating.Exercise for 15 minutes instead of eating, or call a friend to chat.Instead of eating, clean the home or work in your garden.

-- Diana Kohnle

Study Disputes Notion That Breakfast Is Key to Weight Control

THURSDAY, June 5, 2014 (HealthDay News) -- New research refutes the common belief that skipping breakfast could contribute to obesity.

Instead, researchers at the University of Alabama at Birmingham (UAB) found that passing on the first meal of the day doesn't help or hinder efforts to lose weight.

"The field of obesity and weight loss is full of commonly held beliefs that have not been subjected to rigorous testing; we have now found that one such belief does not seem to hold up when tested," senior investigator David Allison, director of the UAB Nutrition Obesity Research Center, said in a university news release. "This should be a wake-up call for all of us to always ask for evidence about the recommendations we hear so widely offered."

The study involved 309 overweight and obese adults between the ages of 20 and 65. The otherwise healthy participants were randomly told to eat breakfast or skip the meal. The study also included a control group that was given healthy nutrition information, but not any specific instructions about breakfast. People in this control group included those who ate breakfast and those who skipped breakfast.

The researchers analyzed the effects of eating or skipping breakfast on weight loss. They also examined how changing breakfast habits could influence efforts to shed unwanted pounds.

"Previous studies have mostly demonstrated correlation, but not necessarily causation," study author Emily Dhurandhar, an assistant professor in UAB's department of health behavior, said in the news release. "In contrast, we used a large, randomized, controlled trial to examine whether or not breakfast recommendations have a causative effect on weight loss, with weight change as our primary outcome."

The study, published online June 4 in the American Journal of Clinical Nutrition, revealed there was no difference in weight loss among the various groups.

"We should try to understand why eating or skipping breakfast did not influence weight loss, despite evidence that breakfast may influence appetite and metabolism," Dhurandhar noted.

Also, the findings only included body weight and did not examine the effects of breakfast habits on people's appetite, body fat and metabolism, she said.

"In addition, our study was 16 weeks in duration, which is longer than many previous studies; but it is not clear whether an effect of the recommendation would be clearer from an even longer duration study," Dhurandhar added. "Finally, we gave subjects a recommendation of what a healthy breakfast is, but left their choices of breakfast foods up to their discretion."

-- Mary Elizabeth Dallas