THE SCIENCE OF FAT LOSS - Seven Research Facts
The Science of Fat Loss - Seven Research Facts
1) HIIT and Moderate-Intensity Exercise Produce Similar Health Benefits
High-intensity interval training (HIIT)— repeated bouts of high-intensity exercise followed by rest— builds fitness quickly. Canadian researchers found that six sessions of high-intensity interval training on a stationary bike increased muscle oxidative capacity (citrate synthase) by almost 50 percent, muscle glycogen by 20 percent and cycling endurance by 100 percent. The subjects made these amazing improvements exercising a mere 15 minutes in two weeks. This study caused a frenzy in the fitness industry, which changed the way many people train. Does HIIT provide the same health benefits as traditional, moderate-intensity training (MIT)? A study led by Gordon Fisher from the Department of Human Studies, University of Alabama at Birmingham, concluded that HIIT and MIT had similar effects on aerobic capacity, body composition, insulin sensitivity, blood pressure and blood fats. Twenty-eight sedentary, overweight men practiced HIIT or MIT for six weeks. The HIIT program consisted of four 30-second sprints on a stationary bike at 85 percent of maximum effort, while MIT consisted of 45 to 60 minutes of cycling at 55 to 65 percent of maximum effort. HIIT produced the same changes in one hour per week as MIT did in five hours per week. (PLoS ONE, 10(10): e0138853, 2015)
2) Is Fasting Healthy?
Many people fast for religious reasons, weight loss or metabolic health. Is it good for you? Fasting regimens include periodic one-day fasts, modified fasts involving caloric restriction and time-restricted fasts involving food restrictions during specific times during the day (religious fasts). A review of literature led by Ruth Patterson from the Department of Family Medicine & Public Health at the University of California, San Diego concluded that fasting reduced blood sugar and insulin, which is linked to chronic type 2 diabetes and heart disease, and caused some weight loss. Fasting is not physically or mentally harmful. However, fasting causes intense hunger, so it is probably not sustainable. Fasting does not result in greater weight loss than sustained calorie-restricted dieting. We don’t know much about the effects of fasting on sleep, hunger control or physical activity. Fasting methods that restrict nighttime eating appear to have positive long-term effects on weight control. Periodic fasting may be a good way to lose weight and promote metabolic health. (Journal Academy Nutrition and Dietetics, 115: 1203-1212, 2015)
3) Bile Acids Help Regulate Energy Expenditure and Weight Control
Recognizing factors controlling the balance between food intake and energy expenditure is important in understanding the physiology of obesity. Energy metabolism works through a series of coupled reactions. This means that energy released by breaking down fats, carbohydrates and proteins is captured in other reactions such as making ATP (a high-energy chemical) or storing fats and carbohydrates. Uncoupling occurs when the energy from food breakdown is released as heat instead of capturing it as ATP. The human body contains small amounts of brown fat and uncoupling proteins that convert energy directly into heat. Polish researchers from the Institute of Animal Reproduction and Food Research at the Polish Academy of Sciences in Warsaw— in a study on rats— found that bile acids produced in the liver as part of digestion triggered uncoupling proteins to increase energy expenditure. This study shows another mechanism the body uses to control bodyweight. (American Journal Physiology Endocrinology Metabolism, published online December 29, 2015)
4) Dietary Fat-Carbohydrate Balance Does Not Affect Growth Hormone Levels
Growth hormone helps regulate fat metabolism. Many people take human growth hormone injections because they trigger fat loss. Can we alter natural growth hormone release by manipulating the composition of the diet? A study led by Hiroto Sasaki from Ritsumeikan University in Shiga, Japan found that three-day diets high in fat and low in carbohydrate, or low in fat and high in carbohydrate, had similar effects on growth hormone levels in healthy men. At the end of each three-day diet, the men rode a stationary bike for 30 minutes at 60 percent of maximum effort. Fat use was higher after exercise when the men had consumed a high-fat, low-carbohydrate diet, but these changes were temporary. Short-term diet modifications have no effect on growth hormone levels in blood. (Growth Hormone & IGF Research, 25: 304-311, 2015)
5) Ketogenic Diets Do Not Impair Muscle Growth
Body fat and proteins break down to produce energy during fasting or carbohydrate restriction. In the absence of adequate dietary carbohydrates, the fatty acids from fat breakdown are incompletely metabolized, which produces ketone bodies and causes ketosis (accumulation of acetoacetate and beta-hydroxybutyric acid in the blood). Fats burn in a flame of carbohydrates. Carbs break down to pyruvic acid, which supplies structures for the Krebs cycle— a critical metabolic pathway for metabolizing fats. Can muscles grow during ketosis— a time when the body is using muscle protein for fuel? A study on rats led by Michael Roberts from the Department of Cell Biology and Physiology at Auburn University in Auburn, Alabama found that rats fed a ketogenic diet (20 percent protein, 10 percent carbs, 70 percent fat) showed similar adaptations to resistance training as animals fed a normal Western diet (15 percent protein, 43 percent carbs and 42 percent fat). If these results apply to humans, this is important information for athletes trying to lose weight by following a low-carbohydrate diet. (Journal of Applied Physiology, published online December 29, 2015)
6) Humans Designed to Move and Eat
Focus on good-quality nutrition and regular exercise if you want to maintain a healthy weight— according to an editorial by Jean-Pierre Després from Laval University in Québec, Canada. Most studies show that dietary restriction is the most important factor in losing weight, and that exercise has minimal effect. However, exercise provides a buffer to combat excess caloric intake. People who lose weight and keep it off typically include large amounts of exercise in their weight-maintenance program. Only about five percent of people who lose a significant amount of weight keep it off for more than one year. Despite these depressing statistics, some people lose weight and manage to keep it off. The National Weight Control Registry keeps track of people who successfully lost more than 30 pounds and kept it off for one year or more. These people share one characteristic in common—they burn an extra 3,000 calories weekly, which means they exercise about one hour daily. Don’t assess your progress by scale weight alone. People who exercise regularly tend to gain lean mass while losing fat. Dr. Després recommended replacing the bathroom scale with a simple and cheap tape measure to assess body circumferences. (American Journal Clinical Nutrition, 102: 1303-1304, 2015)
7) Mobile Body Composition Units Come to the Office Parking Lot
Dual-energy x-ray absorptiometry (DXA or DEXA) is the gold standard for measuring body composition. Until recently, it was not available to most people because the units are expensive and mainly restricted to dedicated research labs. That’s changed. Companies such as FitnessWave and BodySpec offer DXA scans from mobile labs that visit companies such as Google, YouTube, Facebook and Cisco. DXA is widely used to assess the risk and progression of osteoporosis, a progressively worsening condition with aging, but the technique can also be used to assess the composition of soft tissues. DXA works by aiming X-rays at the body at two different energies. A difference in absorption of the X-ray beam at these two energies calculates the bone mineral content and soft tissue composition in the scanned region. DXA machines cost in the tens of thousands of dollars, and are typically found in hospitals and rehabilitation centers, university research labs, and medical and public health research centers. Entrepreneurs have figured a way to bring DXA to your office door. (The Wall Street Journal, December 29, 2015)