Weight-related Research from The American College of Sports Medicine (ACSM)

author : Nancy Clark
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Exercise is medicine. Given that two-thirds of Americans are either overweight or obese, we need to figure out how to turn this ship around.

Exercise is medicine. That was a key messages highlighted at the 2014 Annual Meeting of the American College of Sports Medicine. Given that two-thirds of Americans are either overweight or obese, and that healthcare costs (to say nothing of quality-of-life costs) are staggering, we need to figure out how to turn this ship around. This article highlights some research by ACSM members related to diet, exercise, weight, and health. The info will hopefully remind you that a wise food and exercise program is far better than taking medicine.

• To lose weight, you need to create an energy deficit. But is it true the less you eat, the more weight you will lose? No. A big slashing of calories poorly predicts how much weight you will lose because your body adapts to perceived “famine” conditions by conserving energy.

In a three-month study, young, healthy women were given a diet to lose weight. One diet had a moderate (-400) calorie deficit; this group lost 6 pounds in 3 months. The other diet had a severe (-850) calorie deficit; that group lost only 8 pounds. This was far less than predicted and related to a drop in resting metabolic rate. The body's ability to conserve energy is quite powerful! If you want to lose weight, plan to chip off just a few hundred calories at the end of the day, rather than starve yourself by undereating all day. 

• Men who want to lose weight should not crash diet. They will lose not only muscle but also testosterone (a muscle-building hormone). In a three-week study, soldiers ate a high protein diet (3 x the RDA; 2.4 g pro/kg/day) but underate calories by 40% below the amount needed to maintain weight. While the very high protein intake helped counter loss of muscle, it did not maintain testosterone levels. Remember: chipping off a few hundred calories is preferable to a chopping off a thousand. Two fewer cans of soda or beer a day can make a difference in weight!

• Are dieters better off eating three small meals plus three small snacks—or eating the same amount of calories but in just two meals? For two weeks, obese middle-age women ate calorie-controlled packets of food either two or six times a day. Either way, the subjects reported being hungry. Eating six smaller meals did not appear to improve appetite response. So take your choice how often you want to eat, being sure to keep the total calories within the budget.  

• Many dieters drink coffee for breakfast, swearing it curbs their morning hunger pangs. Yet, a study with 12 subjects reported no differences in appetite (and subsequent food intake) when their breakfast and mid-morning beverages were 1) water, 2) water+caffeine, 3) decaffeinated coffee or 4) decaf+caffeine. At lunch (4.5 hours after breakfast), the subjects reported similar amounts of hunger and ate similar amount of calories, regardless of their caffeine intake. The coffee did not effectively curb their appetites.

• What happens to food intake when healthy college men who exercise regularly are told to sit for 10 additional hours a week for 8 weeks? They eat less! At baseline, the subjects ate about 2,600 calories a day (47% carb, 18% protein, 32% fat). When they were told to be more sedentary, they intuitively ate less than baseline. They chose the same foods, just smaller portions. Only 1 of the 8 subjects ate more than at baseline. The moral of the study: If you get injured and cannot exercise, your body can naturally desire fewer calories. The trick is to listen to your body’s cues, not tempting food ads on TV! 

• Exercise can impact not only weight but also the kinds of microbes that grow in the gut. In mice, the kinds of microbes differ by 40% between sedentary lean and obese mice. Even mice made obese by a high fat diet—but allowed to use an exercise wheel—had a lean phenotype compared to the sedentary obese mice with no access to the exercise wheel. The exercised mice had distinctly different gut microbes. We need more research to understand how exercise impacts gut microbes in humans and how those microbes impact metabolism and weight. 

• Many lightweight rowers have to drop weight during in-season training. Does this hurt their rowing? Likely yes! A study compared the 2K erg performance of 7 heavyweight and 7 lightweight candidates for the US Rowing National Team in December (off-season) and July (in-season). Compared to the off-season, the heavyweight rowers improved their VO2peak/fat-free mass while in-season. The lightweight rowers did not. The dieting rowers decreased total body weight by ~4.5 pounds and body fat by ~1%. They lost about 2 pounds of lean muscle. They rowed slower in the simulated 2,000-meter rowing test. The researchers recommend that lightweight rowers try to maintain their required weight throughout the year, so they can focus on performance during the season. Easier said than done...?

• Female athletes commonly have low bone mineral density. Is this related to their being light in weight? Having low body fat? Less muscle? A study of 44 female D-1 athletes (from cross-country, tennis, basketball and soccer teams) suggests that bone mineral density significantly relates to muscle mass. The more muscle, the better the bone density. Keep lifting those weights!

• Does very slow walking (1 mile/hour) on a treadmill desk offer any health benefits? Yes. In a study, 32 college students consumed 300 calories of glucose and then either 1) remained sedentary for two hours or 2) for two hours, alternated walking on a treadmill workstation for 30 minutes then sitting for 30 minutes. The results suggest even very slow walking helped with blood glucose control. Any exercise is better than no exercise. Being sedentary is deleterious to health.

• The older we get, the less we move. Regular leisure-time exercise patterns drop from childhood to adolescence and become unacceptably low in adulthood. Is this decline related to changes in reward pathways in the brain? Researchers need more information to unravel the genetic pathways that affect exercise behavior. But before too long, we may get personalized strategies, based on our genes that will increase our lifelong desire for exercise. Stay tuned!


Nancy Clark, MS, RD CSSD (Board Certified Specialist in Sports Dietetics) counsels active people at her private practice in Newton, MA (617-795-1875). For more information, enjoy reading her Sports Nutrition Guidebook and food guides for marathoners, soccer players, and cyclists. They are available at www.nancyclarkrd.com. Also see www.NutritionSportsEerciseCEUs.com for online education.


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date: February 27, 2015

Nancy Clark

Nancy Clark, MS, RD, an internationally known sports nutritionist and nutrition author, is a registered dietitian (RD) who specializes in nutrition for exercise, health and the nutritional management of eating disorders.

avatarNancy Clark

Nancy Clark, MS, RD, an internationally known sports nutritionist and nutrition author, is a registered dietitian (RD) who specializes in nutrition for exercise, health and the nutritional management of eating disorders.

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