SUMMER IS ALL about slimming down, which means winter is when you can really build bulk. If you want to make muscle though, you have to start eating more—way more. The problem: Jump straight from a caloric deficit to a caloric surplus, and your body will gain not only muscle but also fat.

“If you want to be in an anabolic state and build muscle, you have to fuel this process with calories. Anabolic reactions are endergonic, which means they must be driven by the input of energy,” explains Bill Campbell, Ph.D., C.S.C.S., director of the Performance & Physique Enhancement Laboratory at the University of South Florida.

But if you go straight from a cut to a bulk—adding, say, 1,000 calories to what you’re eating now—the physique-minded lifter faces two problems. First, your body will hold on to any fat it can come by. Second, you’ll actually be less efficient at making muscle.

Furthermore, after a cut, your catabolic hormones are running high and your anabolic hormones are low, making it more difficult for your body to build muscle, she adds.

To top it off, your body adapts to a caloric deficit by lowering your metabolic rate. “If you throw in a bunch of calories after a dieting phase while your metabolism is suppressed—coupled with your body’s desire to gain fat back after losing it—you’ve entered an environment where much of your post-diet weight gain will be in the form of body fat,” Campbell says.

How to gain muscle but not fat

Luckily, there’s a workaround. It’s called reverse dieting, and it entails slowly increasing your calories over time to bring you out of a deficit, up to maintenance, and then up to bulk.

“Reverse diets circumvent the fat gain because when you only add in a modest amount of calories over time—which you have to be very disciplined about—you allow your body’s metabolism to increase incrementally, [rather than] ‘overshooting’ its ability to deal with these extra calories and then depositing them as fat,” Campbell explains. Just as the incremental increase lets your metabolism reset, it also allows your hormones to balance out, because they’re not being thrashed from one end of the room to the other in a day.

One thing to note: If you’ve been cutting like crazy for an event and now don’t really care if you gain fat, you can totally just shoot straight from calorie deficit to calorie surplus. But the reality is, most of us do care. Plus, going straight from cut to bulk time and time again (like a bodybuilder might) can take a long-term toll on your hormones and ability to lose weight in the future, Smith says.

In other words, like everything else in life, the healthiest and most sustainable way to go about a physical goal is to ease in and be patient.