What is the point of losing weight?
Do you want to lose weight to become more physically attractive? Or to fit into your existing wardrobe more easily? Or to improve your overall health? If your main reason is to improve your overall health, losing weight is probably not your best bet for two reasons. First, the vast majority of people are unable to lose substantial weight (for example, at least 5 percent of body weight) and to keep it off for the long haul. Second, evidence shows that building your cardiorespiratory fitness is a more effective route to improving your overall health.
Wait a minute …
You might object to the idea that building cardiorespiratory fitness is the way to improve your health. You may have heard of a study that revealed minimal weight loss following a program of increased physical activity. If so, you probably heard correctly. (See Lots of aerobic exercise … below for more info.) But the evidence shows that the health benefit of a program to build cardiorespiratory fitness does not arise from any weight loss (maybe minimal) that might occur. Rather, the health benefit arises from improving your body’s ability to deliver oxygen to mitochondria in your cells to release energy.
Five reasons to focus on improving cardiorespiratory fitness
The prevalence of obesity has increased markedly in recent decades and is projected to include almost 50 percent of Americans by 2030. Plus, obesity predicts increased risks of cardiovascular disease and other ills. The typical strategy to avoid or resolve obesity is to lose weight. However, weight-loss is difficult to sustain over the long-haul. Researchers Gaesser and Angadi propose a different strategy, namely improved cardiorespiratory fitness (CRF) through increased physical activity.
The rationale for doing so rests of five points: 1) increased mortality risk predicted by obesity declines or disappears with moderate to high CRF, 2) most cardiovascular markers can be improved with better CRF without weight loss and to a degree comparable to that observed with weight loss, 3) weight loss is not consistently associated with reduced mortality risk, 4) improved CRF or physical activity consistently predicts greater reduction in mortality risk than intentional weight loss, and 5) weight cycling (that is, weight loss followed by weight gain, followed by weight loss, etc.) predicts several adverse health outcomes. This is not to say that making a life commitment to ramp up physical activity is easy for those with obesity. Yet, if people with obesity (or overweight) focus their attention on improving their CRF, they will likely realize major health benefits even if they don’t lose any weight. In addition, embracing the healthy lifestyle choice of Keep Moving directs attention to a highly desirable good (better CRF) rather than a bad to be eliminated (obesity).
Fit but fat
Steven Blair popularized the idea of “fit but fat” reflecting studies that showed subjects who had overweight or obesity but had high cardiorespiratory fitness had lower risk of premature death than subjects who were normal weight but unfit. A meta-analysis in 2014 supported the fit but fat idea. However, that meta-analysis suffered from a statistical shortcoming plus the included studies had very few women. A new systematic review and meta-analysis overcame these defects but still supported fit but fat.
Specifically, compared to subjects who were normal weight and fit, subjects who were overweight and fit or obese and fit did not have significantly higher risk of premature death or death from cardiovascular disease. However, subjects who were normal weight and unfit or overweight and unfit or obese and unfit had significant 192, 182, and 204 percent higher risks of premature death, respectively. For death arising from cardiovascular disease, the comparable increases in risk for normal weight and unfit or overweight and unfit or obese and unfit were 204, 258, and 335 percent, respectively. Importantly, in most of the included studies, fit subjects exceeded only the fitness level of the bottom one-fifth of the overall subject sample, a rather low bar for cardiorespiratory fitness. Presumably, subjects with objectively rather than relatively high cardiorespiratory fitness would fare even better in these comparisons. In addition, greater cardiorespiratory fitness diminishes elevated health risks associated with overweight or obesity.
Lots of aerobic exercise can induce body fat loss
Health providers typically recommend increased physical activity to help patients lose weight. A new systematic review and meta-analysis of 116 randomized controlled trials examined the level of aerobic exercise linked to an amount of weight loss. The included studies featured supervised types and levels of physical activity from 25 Western and 23 Asian countries. Each 30-minutes per week of aerobic exercise predicted a modest but significant 1.1 pound of weight loss. In addition, each 30-minutes per week of aerobic exercise predicted a modest but significant decrease in waist circumference (-0.52 cm) and body fat (-0.37 percent), and visceral fat (-1.6 cubic cm). The biggest reduction in body fat percentage (-2.08 percent) occurred at 150 minutes per week (21.4 minutes per day) of aerobic exercise. Note that a 2.0 percent or greater drop in body fat is considered clinically meaningful. Increases in daily physical activity up to 300 minutes per week (42.9 minutes per day) predicted a 9.2 percent decline in body-fat percentage. These results suggest that a serious, long-term commitment to at least 21 minutes of aerobic exercise per day may lead to clinically significant weight loss.
What about people with overweight or obesity who can’t do aerobic exercise?
The appearance of novel, effective, and expensive GLP-1 agonist weight loss drugs offers an alternative to the current standard of care for patients with overweight or obesity, which begins with a comprehensive lifestyle intervention. Typical components include lower caloric intake, increased physical activity, and behavior change. Alas, dismal the track record for substantial, long-term weight loss may seem to obviate the need for and value of a comprehensive lifestyle intervention. A new Viewpoint in JAMA Internal Medicine argues that, in addition to their poor track record, comprehensive lifestyle interventions are not accessible or practical for many patients with overweight or obesity. Barriers include the lack of physical mobility, lack of proximity to providers of lifestyle interventions, and food insecurity. The Viewpoint authors urge altering the standard of care for overweight and obesity to recommend, rather than require, a comprehensive lifestyle intervention.
What to do
If you have overweight or obesity and want to improve your health, what can you do? One route, especially if you’re unwilling or unable to do aerobic exercise is start taking one of the new GLP-1 agonist drugs, such as liraglutide or semagutide. You’ll need to see a doctor to get approval for a prescription, which may be hard to get unless you also have diabetes. Even if you get a prescription, your medical insurance may not cover the high cost of the drug. Remember that keeping the weight off requires continuing the medication.
Another route is to improve your cardiorespiratory fitness, which would have the added bonus of improving your health. How do you do aerobic exercise? By engaging in activities that substantially elevate your heart rate, to 60 to 80 percent of your maximum heart rate. Broadly speaking you have two options. First, high-intensity, short-duration interval training. Find an activity (such as rowing, cycling, swimming, stair climbing) in which you can exert maximum (or near maximum) physical effort for brief periods of time, say 10-20 seconds. Recover for a minute then repeat the maximum physical effort and rest cycle two more times. Do this program three times a week. Second, longer periods (say, 30 minutes) of vigorous exertion, maybe at 60-80 percent of your maximum heart rate with warm up and cool down. Three times a week. If you go the cardiorespiratory fitness route, I strongly urge you to get checked out first to make sure that your heart can handle the extra exertion.
