Swimsuit season is here, and you want to get your body ready for the beach. Or perhaps that class reunion is rapidly approaching, and you want to be in better shape than your former high school nemesis.

Whatever your reasoning, a crash diet can seem appealing when you want to lose weight quickly. But they are actually a very bad idea, for several important reasons.

Your metabolism will slow. When you cut back your caloric intake to drastically low levels, your body responds as if you’re experiencing a famine. This would be a great mechanism to have in an actual famine, but for those trying to lose weight, it can be frustrating and counterproductive. Your metabolism will slow, as your body struggles to hold onto fat stores. In the best case scenario, you won’t lose as much weight as you’d hoped. In the worst case scenario, you could make yourself sick – or at the very least, quickly regain all of the weight when you abandon your crash diet.

You will drain your willpower. Starvation diets only last so long. They all depend upon willpower, and you will eventually run out of that mental tool. When it’s gone, it’s gone in a big way…. and you will probably find yourself pigging out on every high-fat, sugary snack in sight.

You will deplete your body of essential nutrients. Aside from pure energy in the form of calories, food provides us with vitamins and minerals that we need for optimal health. If you aren’t eating enough, chances are high that you also aren’t getting enough of these essential nutrients. You can actually starve yourself into sickness or chronic health problems. At the very least, you will notice that you feel awful and your skin looks sickly – not the look you’d imagined for your class reunion.

Crash diets distract you from what really works. When you crash diet, you’re relying on a temporary strategy, and you will achieve only temporary results. Focus instead on identifying a healthy diet and lifestyle that works for you, and you can use this time to form good habits that will last a lifetime.