The New Science of More Muscle (and Less Fat)

Men of a certain age are almost always caught between two ideals: We want to build muscle (get bigger), and we want to shed fat (get smaller). These two ideals seem at odds. As a result, we find ourselves heading in one direction or the other, either the fireplug-shaped weight lifter or the beanpole distance runner. What does it take to get muscle and lose fat?

Ian Smith, M.D., has been working on figuring out that problem. A former member of the President’s Council on Fitness, Sports and Nutrition, Smith created a protocol called the Met Flex Diet that incorporates elements of intermittent fasting and keto, weight training and cardio but that avoids the extremes of those methods.

I know I have to eat more calories to build muscle but eat fewer calories to lose weight. How exactly do I do both? 

Guys think, I have to go to the gym, work out and then eat lots of protein. What you really have to do is to match your protein intake to your workout. I have my guys do a bulking phase (muscle building) and a cutting phase (fat burning). 

How do the bulking and cutting phases differ?

It’s as much about meal timing as anything else. It’s based around intermittent fasting — which guys love, because there are simple rules that are easy to follow. What you want is to create at least a 14-hour fast (16 is better), followed by an eight- to 10-hour feeding window. When you’re cutting — losing fat while trying to hold on to the most possible muscle — you want to finish your workout with about two hours left in your fasting window. By that point, your body will have burned through all of its stored glycogen and will be burning fat for the next several hours. If you’re bulking — just focusing on adding new muscle — then you want to finish your workout right before you start eating, so the new energy can be used immediately to build mass. 

Does what I’m eating change depending on the phase I’m in?

When you’re bulking, you want to go very low on carbs — I have my guys follow a keto diet during this time. So plenty of fats, plenty of protein. And during this time, you want to lift weights, but you’re not trying to lift to your one-set max. The new science around weight lifting is that you don’t have to damage the muscle to create growth, you just have to lift to failure. So lift for eight to 12 reps, but heavy enough so that you’re doing it to failure. That’s where the growth comes. 

Then when it’s time to cut, we switch to more body weight exercises, more cardio, more high-intensity interval training (HIIT). And that’s when you can eat the carbs you love. People think they can’t eat carbs if they’re trying to cut weight, but it’s totally fine as long as you’re doing a pretty intense cardio program and keeping your eating windows tight. Those glycogen stores are going to get burned up quick. 

How long is each phase? 

Two days. That’s why guys love this because you’re never bored: For two days you’re having pasta and pizza, and then for two days you’re having burgers and steak. That’s the idea behind “metabolic flexibility,” which is that you’re training your body to burn both fats and carbs at peak intensity. It’s easy, and it gets guys the best of all worlds, no tofu required.

[For more from Dr. Smith, check out his website and follow him on Instagram.]