Exercise is often touted as the ultimate "magic pill" as it has been linked to numerous health benefits and has even been demonstrated to reverse aging at the molecular level in at least one groundbreaking study published in the Public Library of Science. Whether the elusive fountain of youth or not, regular exercise is good for us.
Yet, more recently, the role of exercise in weight loss has come into question. On a very basic level, exercise burns calories and logically speaking, anything that creates a calorie deficit should also assist in our weight loss efforts. The problem seems to be that while exercise does burn calories, it also stimulates appetite, and there have been several studies that show that exercisers tend to overestimate the calories they burn while exercising and underestimate calories consumed while eating. So a 300 calorie deficit which is achieved via a three-mile trek on the treadmill is often rewarded with a 500-700 calorie meal.
Anyone who's ever spent an hour sweating it out on the elliptical has at one point or another marveled at how hard it is to burn calories, but how easy it is to eat them. For example, a single serving of pumpkin pie (about 1/8 of the pie) provides roughly 350 calories, which could take anywhere between 30-45 minutes jogging/running to burn off.
This discrepancy exists because the majority of calories we require in any given day is primarily a function of our basal metabolic rate (calories our body burns to maintain itself) and not our activity.
But doesn't exercise build muscle, and doesn't increased muscle mass increase our metabolic rate?
Actually, the type of exercise recommended for weight loss (aerobic exercise - think jogging, biking, walking) isn't that great at building muscle. Building muscle takes a stimulus (usually a weight and/or load) that overtaxes the system. And building muscle requires adequate recovery, which can sometimes take up to a week or more.
Bottom line, exercise can keep the machine fine-tuned and running smoothly, but contrary to what the mainstream fitness industry claims, as a stimulus for weight loss, it falls short.
For example, a 150 pound person burns approximately 130 calories per mile while running. (Obviously, there is a range but for argument's sake work with me). A person running a marathon will use approximately 3,380 calories. Add to that the post-exercise burn which is estimated to be 10-15 calories for every 100 calories burned during the activity, you get another 500 calories using the larger number. This is a total of 3, 880 calories.
Sounds pretty impressive, right?
Of course, you have to take into account the resting metabolic weight, which represents calories that would have been burned regardless, 60-130 calories per hour for someone who was sitting and 100-200 calories per hour for someone standing. So let's assume that the marathon took about 4 hours to complete (which happens to be the average.) And let's assume that had the runner not been running they would have spent 2 hours in a standing activity and 2 hours in a sitting activity. That's about 480 calories. So the net calorie burn for the runner is now 3,400 calories.
Still impressive you say?
Now let's assume that you, the runner, go out to celebrate your accomplishment. You head over to your favorite Italian restaurant to refuel, because let's face it, running a marathon is a big feat for most people and you not only need those calories, you deserve them. You order the calamari as an appetizer (670 calories), and the eggplant parmigiana as your main course (1060 calories). You usually pass on the breadsticks, but you've just run a marathon for goodness sake. Those glycogen stores aren't magically going to replenish themselves. Still, you limit yourself to one (140 calories). You're not a glutton after all. You also drink two glasses of wine (250 calories). When asked about dessert, you decline. You're stuffed, and no reason to overdo it. Thanks to this one meal you've now replaced 2,120 calories. And this doesn't take into consideration the extra calories you are likely to eat over the next 24 hours. That's a lot of work, time and wear and tear on your body simply to end up with a few hundred calorie deficit, if you end up with any deficit at all.
The moral of this story?
Clearly, exercise is important, so go ahead and run the marathon if that's your thing. Depending on the type of exercise you engage in it can help to build and maintain muscle which protects joints and enhances performance. It can improve cardiovascular fitness, coordination, and flexibility. It can increase our cells' sensitivity to insulin, help to regulate hormones, and boost our metabolism. It can elevate mood, help us manage stress, and promote better, more restorative sleep. It can also help us to maintain a healthy weight as clearly demonstrated by an ongoing initiative called the National Weight Control Registry, a study that originated in 1994. The goal of the registry has been to identify behaviors that are associated with maintaining weight loss. Apparently, just because exercise isn't always a big help when it comes to winning the battle of the bulge, doesn't mean it isn't essential in ensuring we win the war.
You will never out-train a bad diet, so why try. Exercise because it's good for you and the awesome machine that is your body. Period. When it comes to weight loss, focus on your diet, the bulk of which should be non-starchy vegetables, fruits, nuts, seeds, beans, lentils, whole grains, and quality meat and dairy as tolerated. Processed foods, sweets, soft drinks/liquid calories including alcohol, and anything that comes in a box or is made in a plant should be kept to a minimum.