Less TV, More Exercise Are First Steps Toward Achieving Weight Loss
Source: Hu FB, et al. Television watching and other sedentary behaviors in relation to risk of obesity and type 2 diabetes mellitus in women. JAMA 2003;289:1785-1791.
Abstract: Current public health campaigns to reduce obesity and Type 2 diabetes have largely focused on increasing exercise, but have paid little attention to the reduction of sedentary behaviors. The authors examined the relationship between various sedentary behaviors, especially prolonged television watching, and risk of obesity and Type 2 diabetes in women. This prospective cohort study was conducted from 1992 to 1998 among women from 11 states in the Nurses’ Health Study. The obesity analysis included 50,277 women who had a body mass index (BMI) of less than 30, and were free from diagnosed cardiovascular disease, diabetes, or cancer, and completed questions on physical activity and sedentary behaviors at baseline. The diabetes analysis included 68,497 women who at baseline were free from diagnosed diabetes mellitus, cardiovascular disease, or cancer. During six years of follow-up, 3,757 (7.5%) of 50,277 women who had a BMI of less than 30 in 1992 became obese (BMI 30). Overall, the researchers documented 1,515 new cases of Type 2 diabetes. Independent of exercise levels, sedentary behaviors, especially TV watching, were associated with significantly elevated risk of obesity and Type 2 diabetes, whereas even light to moderate activity was associated with substantially lower risk. This study emphasizes the importance of reducing prolonged TV watching and other sedentary behaviors for preventing obesity and diabetes.
Source: Irwin ML, et al. Effect of exercise on total and intra-abdominal body fat in postmenopausal women: A randomized controlled trial. JAMA 2003;289:323-330.
Abstract: The increasing prevalence of obesity is a major public health concern. Physical activity may promote weight and body fat loss. The authors examined the effects of exercise on total and intra-abdominal body fat overall and by level of exercise in a randomized controlled trial conducted from 1997 to 2001. A total of 173 sedentary, overweight (BMI > 24.0 and > 33% body fat), postmenopausal women ages 50-75 years who were living in the Seattle area. Participants were randomly assigned to an intervention consisting of exercise facility and home-based moderate-intensity exercise (n = 87) or a stretching control group (n = 86). Twelve-month data were available for 168 women. Women in the exercise group participated in moderate-intensity sports/recreational activity for a mean (SD) of 3.5 (1.2) d/wk for 176 (91) min/wk. Walking was the most frequently reported activity. Exercisers showed statistically significant differences from controls in baseline to 12-month changes in body weight (-1.4 kg; 95% confidence interval [CI], -2.5 to -0.3 kg), total body fat (-1.0%; 95% CI, -1.6% to -0.4%), intra-abdominal fat (-8.6 g/cm2; 95% CI, -17.8 to 0.9 g/cm2), and subcutaneous abdominal fat (-28.8 g/cm2; 95% CI, -47.5 to -10.0 g/cm2). A significant dose response for greater body fat loss was observed with increasing duration of exercise. Regular exercise such as brisk walking results in reduced body weight and body fat among overweight and obese postmenopausal women.
Comments by Mary L. Hardy, MD
Attempts to meet a major goal of Healthy People 2000 public health initiative (a prevalence of overweight adults of less than 20% of the total population) have failed and failed badly. As of 2000, the majority of Americans are overweight, with 56% reporting a body mass index (BMI) greater than 25.1,2 Sadly, our rate of weight gain has been increasing in the last decade. Obesity, defined as a BMI greater than 30, has increased 65% from 1991 so that now 19.8% of the American population have a BMI greater than 30.1 It has been estimated that the costs of obesity, both in financial terms as well as in development of health problems, is higher than those for either smoking or excessive drinking.3
Perhaps of greatest concern are the effects on our children, who are themselves alarmingly overweight and developing metabolic illnesses not previously seen in children. According to the 1999 National Health and Nutrition Examination Survey (NHANES), 13% of children and adolescents are seriously overweight and are displaying increasing rates of diseases, such as Type 2 diabetes. This bodes poorly for our children in the future. Fontaine and his group reported a loss of years of expected life related to obesity, which was higher the worse the obesity and the earlier it was present.4 Adverse effects also were worse for blacks than whites. For young, severely obese black men (BMI > 45) this translated into 20 years of life lost.
Not only do obese patients have an increased risk of significant illnesses (including hypertension, diabetes, dyslipidemia, syndrome X, coronary artery disease, and certain cancers) and a concomitant decrease in life expectancy, they also suffer from a reduced quality of life.5-7 The higher the degree of obesity, the greater the impairment of health-related quality of life (HLQOL); weight reduction improves HRQOL in the short term.4
Despite the fact that physicians are worried about the adverse effect on the health status of patients, it appears that pain may be the symptom that drives patients’ immediate sense of impaired health.8 This decrease in QOL may be even more severe in children. In fact, children and adolescents with severe obesity report a quality of life that is similar to that of children with cancer.9 Certainly, it is neither medically desirable nor socially acceptable to be overweight. Despite the fact that millions of Americans are dieting, our population just keeps getting fatter. What’s going on?
Recently much attention has been given to adverse changes in our diet, especially the increased consumption of high fructose corn syrup (236% in last 20 years), increased amounts of food consumed away from home, and increased plate and portion sizes at restaurants.10 However, we don’t always pay as much attention to the other side of the energy equation—not the increased intake of energy, but the rate of use of calories. The two articles we are examining today investigate exercise as a factor in creating and modifying obesity and its attendant risks.
Hu and associates followed a very large cohort (n = 50,277) of non-obese women from the Nurse’s Health Study for more than six years. During the six years in which they were observed, 7.5% of the women became obese and 40% of these obese women developed Type 2 diabetes. Sedentary behavior was strongly correlated with an increase in both weight gain and risk of diabetes. The risk of sedentary behavior was paradoxically independent of exercise, although in women who exercised, the rate of weight gain and diabetes was less. All kinds of sedentary activities were not equivalent in their negative impact.
Watching television (TV) was most strongly negatively correlated with weight gain and risk of diabetes and was associated with higher risk of adverse outcome than other sedentary activity at home or at work. For each 2 hr/d increase in TV watching, subjects showed a 5% increase in weight gain and 7% increase in risk of diabetes. Further, those who watched more TV were also more likely to smoke and drink alcohol and were less likely to exercise. They also took in more total calories and made less desirable food choices (higher in fat, meat, and sweets; lower in fish, vegetables, fruit, and whole grains).
The authors offered interesting comments about why TV watching was such a pernicious type of sedentary behavior. First, if you are watching TV you generally are not doing something active—thus substituting a passive for an active activity. TV watchers also tend to eat while watching TV, thus increasing calorie intake, and tend to follow a less healthy eating pattern, which has been shown to be directly related to the types of advertisement and food cues present on TV. Which one of us hasn’t seen the food ads for pizza, burgers, and other fast, high-fat food aired during the dinner hour? Finally, TV watching uses even less calories than other sedentary activities, such as reading a book, sewing, or doing office work. In conclusion, the study authors felt that 30% of the obesity cases and 43% of the Type 2 diabetes cases were potentially preventable if subjects would have followed a relatively active lifestyle characterized by watching TV less than 10 hrs/wk and walking at least 30 min/d.
However, the question remains—can exercise decrease weight and modify the health risks of obesity in women? The second article, by Irwin and colleagues, examines the effect of moderate-intensity exercise on 173 sedentary, obese (mean BMI = 30.9) postmenopausal women—a group that has notorious difficulty losing weight. All of these women had significant amounts of total body fat (47.6% on average) with large stores of intra-abdominal fat (147.6 g/cm2). Patients were randomly assigned to an exercise group (45 min of moderate-intensity exercise for 5 d/wk) or to a stretching control group (similar time).
Support for the exercise group was robust. For the first three months of this year-long trial, women were required to attend exercise classes three times per week, under the supervision of an exercise physiologist, followed by a nine-month at home program. Additional attention was given to the experimental group to ensure continued adherence to the exercise regimen, including behavior change education, phone calls, and individual meetings. Disappointingly, the total weight loss in this study of the experimental group was small (0.5 kg) and barely significantly different than the control group, which gained 0.7 kg. However, significant decreases were seen in percentage of total body fat and amount of intra-abdominal fat in the exercise group vs. the control group. Interestingly, the BMI of the groups were not significantly different at the end of the intervention, highlighting the weakness of BMI as a sole indicator of changes in obesity status.
But is the change in abdominal fat a clinically significant outcome? It probably is because not all fat is created equal when it comes to cardiovascular risk. The presence of abdominal body fat has been correlated more highly with an increased risk of heart disease and insulin resistance than fat in other locations. Likewise, intra-abdominal fat is highly active, secreting intermediary agents, such as cytokines, which promote inflammation. The Diabetes Prevention Program has reported that loss of 5% of total body weight is necessary for a decline in risk of heart disease and diabetes. But, there may be benefits to be realized by a change in distribution of body fat as well as by a decrease in total body fat. A randomized clinical trial of 120 sedentary, postmenopausal women showed that a lifestyle intervention, consisting of dietary advice, exercise training, and support, lead to healthy changes in dietary habits and significant weight loss. In addition, the weight loss was associated with a decrease in inflammatory markers, including cytokines, interleukin 6, and C reactive protein.11 No direct measurement of intra-abdominal body fat was made, but the decrease in the hip-to-waist ratio (a surrogate measure for changes in abdominal fat) was greater in the treatment group than in the control group. Decreases also were seen in blood pressure, insulin sensitivity, and serum glucose. Serum lipids also were influenced favorably with a decrease in triglycerides and low-density lipoprotein with an increase in high-density lipoprotein. So, in fact, the change in body fat distribution reported by Irwin et al likely could represent a significant gain in health for these previously sedentary, postmenopausal women, even without a large weight loss.
How can clinicians use the research results summarized here to help patients? First, we must be willing to address the weight issues of patients. Only 42% of obese people reported that their doctor recommended weight loss when they were asked by researchers.12 Encourage patients that even relatively small changes in weight (5% of total body mass) or decrease in inches around the waist can confer significant health benefits. Measure hip-to-waist ratios, lipids, blood pressure, insulin sensitivity, etc. so that you will be able to point to other things besides just a drop on the scale as a measure of success. Physicians also can let patients know that their quality of life will go up as their weight comes down, and for patients who suffer from pain as a result of weight, quality of life improvement will be especially noticeable to them.
Don’t just focus on the food denial message, also stress exercise as a positive intervention to aid health. Set a goal of 30 minutes most days of moderate intensity exercise. This reasonable goal should be a relief to patients who feel overwhelmed by attempting a huge change. Remind them that any increase in activity at home or at work pays off and steer them away from especially risky behavior like excessive TV watching. Increase the likelihood of a successful intervention by recommending that patients take a class, join a gym, or get a trainer for at least the first 3-4 months. Finally, for patients with children who are overweight, the emphasis on exercise, if it extends to the whole family, can be especially beneficial to the children as they are exposed to positive health choices that may last a lifetime.
Dr. Hardy is Medical
Director, Cedars-Sinai Integrative Medicine Medical Group, Los Angeles, CA.
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