How Long Does It Really Take to See Fitness Results?

In a perfect world, weight loss or, more specifically, fat loss, would be instantaneous. But that's not how the human body works. Instead, everything from your hormones to neurologic system and signals adapts to every little change in your diet and exercise routine.

And, when you change things too drastically, like when you cut your daily food intake from 2,500 to 1,200 calories per day or try to tackle an hour long boot camp class on day No. 1 of your gym membership, your body's adaptations do more harm than good, says Grant Weeditz, a certified strength and conditioning specialist at Anatomy 1220 in Miami.

Your body perceives that food is in short supply, you're starving and, in an effort to spare calories, it starts burning protien (aka muscles) for energy. "This will shut down the fat-burning metabolic processes of the body and start the downward spiral of metabolic damage," Weeditz says. "The more you cut calories, the more you have to continually cut to see results. Avoid this situation like the plague."

What's more, this reduction in resting metabolic rate (the number of calories you burn just to live) means that fast weight loss generally doesn't stick around for long and instead leads to rebound weight gain, explains Atlanta-based board-certified sports dietitian and registered dietitian Marie Spano. For example, in the one University of California–Los Angeles review, about two-thirds of dieters who successfully lost weight ended up gaining back everything they lost – and then some – within four to five years. The psychological effect of depriving yourself or over-exercising in the name of weight loss doesn't help you keep weight off over the long term either.