This Is the Most Weight You Can Safely Lose In A Month By Only Changing Your Diet

This article was written by Allison Young and provided by our partners at Prevention.

So, how much weight can you safely lose in a month by changing only your diet? We desperately wanted the number to be big. Because when you finally decide to lose weight—those pounds that have been slowly, steadily creeping up, pushing you way past wedding dress weight into fat pants territory—you want it to vanish quickly (poof!).

We hate to be the bearer of bad news, but that's not how weight loss works, at least the lasting kind. "Aim to lose 450-900g a week for long-term weight loss," says Marissa Lippert, author of The Cheater's Diet and owner of Nourish Kitchen + Table in New York City—that's 1.8kg to 3.6kg in a month or about a half a dress size.

Oh, and crash diets that promise you'll lose 30 pounds (13kg) in 30 days don't work—drastically slashing calories can sabotage your efforts, ultimately stalling weight loss. "Your metabolism is going to slow down because it's not getting the fuel it needs to burn calories efficiently," says Lippert, who warns women not to go below 1,200 calories a day. Science agrees: Research shows that calorie-restriction plans often fail, with one-third to two-thirds of dieters regaining more weight than they lost on their diets.

You know what else fails? Calorie counting. Sure, it can ultimately whittle your waist—500g of weight is equivalent to 3,500 calories, so skimming 500 calories a day means about 500g a week—but number-crunching every meal is tedious and time-consuming and can take the joy out of eating. "If you get wrapped up in the numbers, it's very hard to sustain long-term changes," says Lippert. "Focus on eating whole foods instead and the calories will fall into place as they should."