why does exercise help you lose weight

One of the main problems with exercise and weight loss is that exercise doesn t just affect the calories out side of the energy balance equation. It can also affect levels, which may cause you to eat more calories. One of the main complaints about exercise is that it can make you hungry and cause you to eat more. It s also been suggested that exercise may make you overestimate the number of calories you ve burned and reward yourself with food. This can prevent weight loss and even lead to
(, ). Although it doesn t apply to everyone, studies show that some people do eat more after working out, which can prevent them from losing weight (, ). Physical activity may influence ghrelin. Ghrelin is also known as the hunger hormone because of the way it drives your appetite. Interestingly, studies show that appetite is suppressed after intense exercise. This is known as exercise anorexia and seems tied to a decrease in ghrelin. However, ghrelin levels go back to normal after around half an hour. So although there is a link between appetite and ghrelin, it doesn t seem to influence how much you actually eat ( ).


Studies on calorie intake after exercise are mixed. It s now recognized that both appetite and food intake after exercise can vary between people (, ). For example, women have been shown to be hungrier after working out than men, and leaner people may become less hungry than obese people (, ). Bottom Line: How exercise affects appetite and food intake varies between individuals. Some people may become more hungry and eat more, which can prevent weight loss. + =. But did you ever wonder exactly why working out helps you lose hungrier)? a mystery even to the medical community, but a new study, Cancer Institute and Harvard Medical School, has helped clarify exactly elliptical. In a nutshell -- exercise causes your muscles to tell your white fat to turn into brown fat. What s that? You didn t know your muscles could talk to your fat cells? And what the heck is the difference between white fat and brown fat? We ll explain. Dr. Aaron M. Cypess, MD, PhD, a researcher and staff physician the Joslin Diabetes Center, broke it down for us: White fat is thusly named because animal fat is, indeed, white. (Cypess says human white fat is actually kind of yellowish -- gross. ) The main purpose of white fat, says Cypess, is to store an enormous amount of calories in a small amount of space.


This, says Cypess, was very helpful when we roamed the plains and needed fat to keep from starving to death in between our scarce meals. Not as helpful these days, when we have unlimited access to calories -- though a little bit of white fat is necessary to live. Having zero fat, as with anorexia, causes all sorts of things to go haywire, says Cypess, but the problem most of us face is having too much. The more white fat you get, the more likely you are to develop health problems like diabetes and heart disease, Cypess says. OK, so what about this mysterious brown fat? Brown fat stores calories not for future use as an energy supply, but as fuel to burn off when it s activated, Cypess explains. He likens white fat to a huge gas tanker storing an enormous amount of fuel, while brown fat is a Lamborghini -- it has gas in it because it needs it to run.


Brown fat burns off calories specifically to generate heat, says Cypess, and it can do that in response to cold, or, it seems, in response to muscular activity (though further research is needed to prove this, says Cypess). What s exciting about the Dana Farber study is that, for the first time, researchers discovered that when you exercise, your muscles release a hormone the researchers named irisin (after Iris, the Greek messenger goddess). And what does irisin do? Cypess describes it like this: It goes to the fat that is under the skin and induces it to grow more brown fat. So how can brown fat help you lose weight? Eat a little bit less, and exercise more, Cypess says, explaining that not only does exercise release irisin, but working out causes your muscles to work harder, which keeps them active after you stop exercising (meaning, you re still burning calories later on). The bottom line? Exercise increases your brown fat levels and brown fat burns calories rather than storing them -- keeping you not just slimmer, but healthier.

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