Donnelly, J.E., et al. 2009. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Medicine & Science in Sports & Exercise, 41 (2), 459-71.
The recent American College of Sports Medicine (ACSM) position stand on physical activity intervention strategies for weight loss reflects an update from the previous guidelines, synthesizing all published data–based research from 1999 to the beginning of 2009.
This compilation of physical activity and weight management research includes individuals ≥18 years of age, although the authors note there is a need for more weight loss studies on older populations (≥65 years). Investigations involving subjects with disorders such as cardiovascular disease, hypertension and type 2 diabetes are included because these health troubles are reflective of the overweight/obese U.S. society. The quantification of exercise intensity is presented in the form of METs (metabolic equivalents of a task). One MET is the equivalent of 3.5 milliliters per kilogram (of body weight) per minute (ml/kg/min) and is considered a resting level of oxygen
consumption. Light-intensity activity is quantified as 1.1–2.9 METs, moderate-
intensity activity as 3.0–5.9 METs and vigorous activity as ≥6 METs.
Presently, 66.3% of U.S. citizens are either overweight (body mass index [BMI] = 25–29.9 kg/m2) and/or obese (BMI ≥ 30 kg/m2). In these people, weight loss of as little as 3%–5% of body weight (although a 10% reduction is encouraged) has been shown to improve high-density lipoproteins (the good cholesterol) and glucose metabolism, while decreasing triglycerides (blood fats) and other risk factors of cardiovascular disease (Donnelly et al. 2009). However, despite these impressive health benefits from weight loss, it is clear that the U.S. is not going to reach its Healthy People 2010 initiative for reducing the prevalence of obesity (see the sidebar “Initiatives and Campaigns to Reduce Obesity”).
and the Prevention
of Weight Gain
In the new ACSM position stand, weight maintenance is defined as a <3% change in body weight, whereas an increase of >5% in body weight is considered clinically significant. (The term clinical implies a medical observation, treatment, practice or diagnosis.) It is clear from all of the research and from leading medical/scientific organizations (Centers for Disease Control and Prevention, ACSM, the American Heart Association and the American Medical Association) that more physical activity is needed for most persons. The recent research indicates that 150–250 minutes per week of moderately vigorous physical activity, at an energy equivalent of ~1,200–2,000 kilocalories (kcal) per week (about 12–20 miles per week of jogging or running), is sufficient for preventing weight gain greater than 3%.
It is recognized that most studies showing clinically significant weight loss (5% of body weight) demonstrate this using
energy restriction (i.e., eating fewer calories) combined with physical activity to create a larger negative energy balance (i.e., more calories expended than consumed). That noted, the research shows that physical activity lasting <150 minutes per week has a minimal effect on weight loss. Physical activity lasting >150 minutes per week usually results in modest weight loss (defined as ~2–3 kg), while physical activity lasting 225–420 minutes per week results in the greatest weight loss (5–7.5 kg).
After Weight Loss
It appears that most individuals are capable of losing weight, with the long-standing challenge being how to maintain the reduction. Consistent physical activity is the best predictor of sustained weight management following weight loss. And, when it comes to preventing weight regain, this position stand reports that some research specifies that study subjects who had lost >10% of their body weight after 24 months were participating in 275 minutes of physical activity per week. However, due to research methodology design flaws, there is currently no definitive answer as to how much exercise is needed to prevent weight regain. Donnelly and colleagues suggest that approximately 60 minutes per day (about 4 miles/day) at a moderate intensity is a likely minimum.
vs. Lifestyle Forms
of Physical Activity
Lifestyle forms of physical activity include types of movement that are not organized approaches to exercise. Lifestyle forms comprise the spontaneous physical activities an individual does during the day (e.g., walking from the car to a store, walking to the chair at a theater, walking in a grocery store, etc.). On the other hand, lifestyle approaches include participation in organized exercise, leisure time physical activity, occupational physical activity, household physical activity and physical activity for commuting (e.g., bicycling). Numerous studies point out that lifestyle approaches to increased physical activity are quite effective for preventing initial weight gain. Unfortunately, most adults spend most of their time sitting. The more active a person is, the less likely it is that he or she will become obese.
Most studies demonstrate that when diet (caloric restriction) and physical activity are combined in a weight management program, weight loss results are encouraging. Donnelly and colleagues (2009) explain that a weight loss program design may create an energy deficit (e.g., 500–1,500 kcal per day) composed of exercise (e.g., 250 kcal per day) and caloric restriction (e.g., 250 kcal per day) for the daily caloric deficit total (500 kcal in this example). In studies where investigators introduce an energy deficit of 700–1,000 kcal per day, “diet only” and “diet plus exercise” result in similar losses. Donnelly explains that this is due to metabolic adaptations that “diminish any additive effect of the energy expenditure from physical activity on weight loss.” However, in investigations where the energy deficit is 500–700 kcal per day, the “diet plus exercise” group sees more weight loss, by about 20%, than the “diet only” intervention.
Consistent resistance training provides numerous health-related benefits, including increases in insulin sensitivity, higher levels of HDL-C (the healthy cholesterol), reductions in blood glucose levels, lower levels of LDL-C (the bad cholesterol) and cardiovascular-disease risk reduction. The increase in muscle mass from resistance exercise has been shown to elevate resting metabolic rate in some persons. Some resistance training programs elicit increased fat oxidation (burning) after the workout (as the body uses additional energy to restore cell processes to homeostasis). Exercise programs combining aerobic training and resistance exercise exhibit superior results for weight and fat loss. In “diet plus resistance training” programs, the addition of resistance training promotes the preservation and/or increase of fat-free mass.
As exercise professionals, the evidence continues to mount that our first goal is to get clients active, with continuing efforts to get students doing more endurance exercise at a more challenging intensity. Regular resistance training is a must for the maintenance and/or increase of fat-free mass. Donnelly et al. (2009) recommend 250–300 minutes per week (~2,000 kcal per week) of moderate-intensity exercise for greater weight loss and prevention of weight gain. We can do it!
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