Written by justis berg
29 March 2010

MD Fat Bytes

By Steve Blechman and Tom Fahey, Ed.D.

 

Low Carbohydrate Diets Linked to Long-Term Psychological Problems

            Losing weight is psychological torture for most people. The long-term success of weight loss diets depends on the psychological capacity to eat less food. Australian researchers found that people following low-fat diets (LF; 46 percent carbohydrate, 24 percent protein, and 30 percent fat) were psychologically healthier after 12 months than those following low-carbohydrate diets (LC; 35 percent protein, 61 percent fat, 4 percent carbohydrate). Both groups ate reduced-calorie diets (1,433 calories per day for women and 1,672 calories per day for men) and lost similar amounts of weight (30 pounds).

            At 12 months, the low-carb group scored higher in measures of depression, anxiety, anger-hostility, tension, and dejection. The LF group showed less fatigue and better all-around mood. Reduced-calorie diets that are either low or high in carbohydrates produce similar weight loss after a year, but long-term adherence to a low-carbohydrate diet produces more psychological side effects. (Archives Internal Medicine, 169: 1873-1880, 2009)

 

Are Your Genes Keeping You From Getting Into Your Jeans?

            Genes play an important role in regulating bodyweight, appetite, and metabolic rate. It seems as though some people can eat whatever they want and not get fat, while others have trouble losing weight even when they eat normally.

            Delores Corella from Tufts University in Boston and co-researchers found that people with a variant (polymorphism) of the APOA2 gene (CC genotype) showed a disproportionate gain in body mass index (proportion of weight to height) when they ate more saturated fat in their diets. However, they only became obese when they ate excessive amounts of saturated fat. Saturated fat intake was less significant in boosting body mass index in people with other variants of the gene (i.e., TT and TC genotypes).

            The study showed that genes make some people more prone to obesity than others, but that behavioral factors, such as reducing fat intake, could compensate for “fat genes.” (Archives Internal Medicine, 169: 1897-1906, 2009)

 

Regular Exercise Causes Weight Loss Without Dieting

            The role of exercise in weight control is controversial. Most studies show that a combination of caloric restriction and exercise are best for weight loss and weight maintenance. However, other studies showed that some people could lose a substantial amount of body fat through exercise alone.

            Buck Willis from Landmark Medical in Austin, Texas and colleagues found that people who exercised at a moderate intensity for 30 minutes, four or more days a week for eight weeks lost 13 pounds of fat in eight weeks. Fat loss was insignificant in those who exercised three days per week or less. The subjects were instructed to consume their normal diet. The exercise program followed the 1996 recommendations of the U.S. Surgeon General and are consistent with the more recent recommendations of the U.S. Department of Health and Human Services. This was only an eight-week study, so the results might not apply to long-term weight control. (Journal Strength and Conditioning Research, 23: 2377-2380, 2009)

 

Is Diet or Exercise Best For Weight Loss?

            If present trends continue, 43 percent of Americans will be obese in just eight years. Obesity is contributing to the public health nightmare in the United States. In spite of spending more money per capita on medical care than any other country, we rank 31st in the world in life expectancy and 19th in deaths from preventable conditions such as obesity. Experts have argued vigorously about the causes of the obesity epidemic. Some say that physical inactivity is the culprit, while others claim that increased caloric intake is the cause.

            Critics of the physical inactivity hypothesis claim that the caloric expenditure from exercise is not significant enough to trigger widespread obesity. An editorial by James Hill in the journal Obesity and Weight Management stated that both caloric restriction and exercise are necessary for weight control, and that concentrating on only one factor is dumb. (Obesity Weight Management, 5: 195-196, 2009)

 

Liraglutide Reduces Body Fat Better Than Orlistat

            Orlistat is a prescription weight-loss drug approved by the U.S. Food and Drug Administration. It works by decreasing fat absorption during digestion. It is sold by prescription as Xenical or over-the-counter as Alli. Liraglutide improves blood sugar control and promotes weight loss.

            A Danish study found that Liraglutide caused greater weight loss, decreased blood pressure, and improved blood sugar control better than orlistat or a placebo (fake drugs). Subjects were asked to decrease food intake by 500 calories per day and increase daily physical activity during the 20-week study. Some subjects in the Liraglutide group experienced nausea and vomiting, but the side effects were temporary and did not cause people to drop out of the study.

            Liraglutide is an effective drug for promoting weight control and metabolic health. It is currently approved in Europe but not in the U.S. (Lancet, in press; published online October 2009)

 

Inadequate Sleep Linked to Obesity and Physical Inactivity

            The recession has led to increased stress, overwork, and reduced sleep. In addition to triggering fatigue, inadequate sleep makes it more difficult to exercise, which promotes obesity. A review of literature by Sanjay Patel from the Case Western Reserve University in Cleveland, Ohio concluded that inadequate sleep promoted obesity, even in people without sleep apnea (obstructive breathing during sleep).

            Sleep duration has decreased by 15 percent since the 1950s, and 16 percent of Americans get less than six hours of sleep per night. Large population studies showed a clear inverse relationship between hours of sleep and the incidence of obesity. However, in spite of the relationship, we cannot say for sure whether inadequate sleep causes obesity.

            Donald Watenpaugh from the University of North Texas Health Science Center in Fort Worth, Texas, said that humans evolved as athletes who sleep 8 to 9 hours per night. Interfering with sleep decreases exercise capacity and threatens metabolic health, which leads to obesity. Sleep is essential to normal energy balance and weight control. (Current Sports Medicine Reports, 8: 331-338, 2009; Obesity Reviews, 10 (supplement 2): 61-68, 2009)

 

Eating Quickly Stimulates Overeating

            Your mother told you to chew your food slowly and enjoy your meal. Many overstressed people often try to eat their food as quickly as possible. They should have listened to their mothers. Greek researchers found that eating a meal quickly decreases hormones in the gut that signal the feeling of fullness to the brain. This can cause overeating.

            During the study, the subjects ate a large bowl of ice cream at different rates and measured the hormones PYY and GLP-1, which help signal the feeling of fullness to the satiety center in the brain. People had higher levels of the hormones and felt more full when they ate the ice cream slowly. Eating meals more slowly may be a simple way to cut down on food intake and decrease body fat. (Journal Clinical Endocrinology Metabolism, in press; published online November 4, 2009)

 

Two-a-Day Workouts Increase Fat Use

            Exercising below 65 percent of maximum effort uses mainly fat as fuel. Above this intensity, carbohydrates become increasingly important, and they're used almost exclusively for fuel at extreme exercise intensities.

            Swiss researchers found that fat use during exercise is influenced by prior physical activity. Moderately-trained subjects took two maximal treadmill tests: one to determine maximal oxygen uptake and estimate fat use and a second to determine the effects of prior exercise on fat use. During the second test, subjects exercised on a treadmill for one hour at 57 percent of maximum effort. After a short break, they took the second treadmill test to exhaustion. Fat use was higher when the subjects took the test after the initial one-hour run. Two-a-day workouts will trigger more fat-burning during the second workout. (Metabolism Clinical and Experimental, 58: 1778-1786, 2009)