Weight Loss Myth Busting with Dr. Karp
Ever wonder if there really is a fat-burning zone? And how much is body weight determined by nutrition and by exercise? And what really is the best diet? Do you know your weight-loss facts from fiction?
Myth: You have to exercise in your fat-burning zone to burn fat and lose weight.
People often assume that low-intensity exercise is best for burning fat. Cardio equipment manufacturers contribute to this assumption by posting a “fat-burning” workout option on their front panels, which influences people to choose that option because, after all, people want to burn fat. During exercise at a very low intensity, such as walking, fat does account for most of the energy you use. At a moderate intensity, such as running at 80 percent of your maximum heart rate, fat accounts for only about half of the energy you use. While you use both fat and carbohydrate for energy during exercise, these two fuels provide that energy on a sliding scale—as you increase your intensity, the contribution from fat decreases while the contribution from carbohydrate increases. While you use only a minimal amount of fat at higher intensities, the number of calories you use per minute and the total number of calories you expend are much greater than when you exercise at a lower intensity, so the amount of fat you use is also greater. What matters is the rate of energy expenditure rather than simply the percentage of energy expenditure derived from fat. Since you use only carbohydrate when you exercise at a high intensity, does that mean that if you run fast, you won’t get rid of that flabby belly? Of course not. Despite what most people think, you don’t have to use fat when you exercise to lose fat from your waistline.
Myth: Working out first thing in the morning on an empty stomach burns more fat.
Muscles will indeed use more fat if you exercise when your blood glucose is low, as it can be first thing in the morning after an overnight fast. But burning more fat during your workout doesn’t necessarily mean that you will lose more weight. Exercising when fasted before breakfast may help you reduce the total number of calories you consume throughout the day, but it doesn’t allow you to cheat the laws of caloric balance; at the end of the day, you still have to have a caloric deficit to lose fat.
When you exercise first thing in the morning before breakfast, your muscles don’t just rely on fat immediately. When exercising at a low or moderate intensity, they’ll use some fat, just like they would when you exercise at any other time of the day. But they’ll also use whatever carbohydrate is available from blood glucose and stored glycogen because carbohydrate is the muscles’ preferred fuel. When you run out of glucose, your muscles will then start to rely more heavily on fat. But exercising on an empty stomach with low blood glucose decreases the intensity at which you can exercise, which results in a lower-quality workout and less total calories burned. For weight loss, it really doesn’t matter if the calories you burn when you exercise come from fat or carbohydrate; how many total calories you burn is what matters.
Myth: Intense workouts contribute to weight loss by burning more calories after the workout is over.
Ever since the fitness industry found research showing that people burn calories after they work out while they recover from their workout, a whole new argument was born. Exercise stopped being about the exercise and became about what came after. “Do this workout,” trainers and gurus say, “because you’ll burn four times as many calories for up to 48 hours afterward.”
After some workouts, specifically those that are intense or long, you continue to use oxygen and burn calories because you must recover from the workout, and recovery is an aerobic, oxygen-using process. This increased oxygen consumption following the workout is called the EPOC (Excess Postexercise Oxygen Consumption).
Many studies have documented the EPOC and compared it and its associated post workout calorie burn between exercise of different intensities and durations. However, the post workout calorie burn caused by the EPOC is a highly overexaggerated issue among fitness trainers. The increase in metabolism is transient, perhaps lasting a few hours, depending on how intense the workout was. The unbridled optimism regarding the EPOC in weight loss is generally unfounded. Studies have shown that the EPOC comprises only 6 to 15 percent of the net total oxygen cost of the exercise, and only when the exercise is very intense. Since unfit individuals recover more slowly than fit individuals, the EPOC will be higher in unfit individuals. However, most unfit individuals simply can’t handle the intensity of exercise that is required to induce a high or prolonged EPOC.
The calories you burn when you exercise have a greater effect on your body weight than the calories you burn afterward. It is the workout itself that creates the demand for change.
Myth: Nutrition (diet) is more important than exercise for losing weight and looking good.
I hear a lot in the fitness industry about the importance of clean eating. Indeed, most fitness professionals quote that physical appearance is 80 percent due to nutrition and 20 percent due to your workouts. I don’t know where those numbers come from, but those percentages are unknowable.
If we are to assign a relative importance to each, it’s presumptuous to think that the specific foods we eat are more important to our health, fitness, and cosmetics than are genetics and training. People like to claim that abs are made in the kitchen, but the truth is that muscles are made by training them. I’m pretty sure I didn’t get my sculpted legs and ass from eating kale salads; I got them from running 6 days per week for 33 years. This is not to say that a person’s diet doesn’t matter. Of course it does. But to place such a large emphasis on diet over exercise misses an important point—cutting calories and eating a more nutritious diet does not make you fitter. Although your nutrition is undoubtedly important, it doesn’t give your muscles a stimulus to adapt. Only exercise can do that and thus give you all of the fitness and health benefits. The sculpted legs of runners and upper bodies of fitness magazine models didn’t get that way just by eating fruits and vegetables.
Truth is, you need both diet and exercise. Diet gets your weight off, especially initially, and exercise keeps it off. To lose weight, you must consume fewer calories each day. To maintain weight, you must exercise on most, if not all, days of the week. Research has shown that body weight and body mass index are directly proportional to the amount of exercise people do.
If we take two people, and one eats perfectly clean with a nutrient-dense diet and no processed foods but doesn’t exercise much, and the other exercises a lot but has a mediocre diet with the occasional Twinkie or chocolate chip cookie, who is going to look better and be fitter? I hope you said the latter. Truth is, exercise and genetics exert a greater influence on how you look (and on your physical performance) than your diet does.
A competitive runner since sixth grade, Dr. Jason Karp quickly learned how running molds us into better, more deeply conscious people, just as the miles and interval workouts mold us into faster, more enduring runners. This passion that Jason found as a kid placed him on a yellow brick road that he still follows all these years later as a coach, exercise physiologist, bestselling author of 8 books and 400+ articles, speaker, and educator. He is the 2011 IDEA Personal Trainer of the Year. His REVO₂LUTION RUNNING™ certification has been obtained by fitness pros and coaches in 20 countries.
Catch Dr. Karp at FitnessFest Anaheim on August 25 & 26, 2018. He'll be presenting his complete 'Weight Loss Myth Busters' lecture on Saturday. Register by August 1st for just $39 or stay all day for $89 (8 CECs!).