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Build muscle, lose fat: Can both occur at the same time?

Fairly common goals I hear are gaining muscle mass, losing fat mass, or both. But can we gain muscle and lose fat at the same time? It’s this scenario about which I usually have to have a practical discussion with my clients, and here’s why…

What Builds Muscle?

I can’t get enough of the Taco Bell protein commercial where they take advantage of mocking the ubiquitous idea that lots of protein is good, and even more is better. While this theme may once have only been pervasive in the bodybuilding arena, it has definitely gone mainstream. So let’s talk about protein for a second.

We don’t really have a storage space for excess protein (unless you count your muscles as storage, and we don’t really ever want to “tap into” those for energy.) Once protein has played its part in repairing muscle and contributing to building things like hair, skin, nails, enzymes, and hormones, whatever is excess in the diet will be converted to energy or stored as fat. And protein is an inefficient and expensive energy source (literally – high protein foods like meat are some of the most expensive items per volume in the grocery store.)

For an athlete, a protein intake of 1.2 – 1.7 grams/kg bodyweight is appropriate, with suggested intakes varying slightly based on sport. To give you an idea of amounts, a 170lb triathlete may need roughly 105-115 grams of protein per day. Intakes higher than 2 grams/kg bodyweight have shown no further benefit for muscle building.

Just having the appropriate amount of protein in your diet won’t guarantee muscle growth, though – and this is where activity comes into the equation. Resistance work is the predominant predictor of the muscle building equation.

Strength Training + Proper Nutrition = Muscle Protein Synthesis

Proper nutrition, of course, includes protein intake, but it’s also about calorie intake in general. Building muscle is an anabolic process and it requires energy, not just protein. So the intake of appropriate amounts of carbohydrate and fat also become very important. Frequently protein intake is over the top, while carbs and fat are inadequate. Carbs provide the energy for the working muscles to do the tough, but necessary, workouts. Therefore, they actually spare protein from being used as an energy source so it can get down to doing its true job.

What contributes to fat loss?

Losing adipose tissue, or fat mass, is actually the opposite end of the spectrum. You are trying to breakdown and use stored energy (fat) rather than build something up (muscle), and to do so there needs to be some sort of caloric deficit. A major caloric deficit is likely to inhibit any muscle growth, with the exception of untrained individuals (more on that later). Yes, you may reduce fat mass and appear more toned and muscular, but that does not necessarily equate to muscle gains. In fact, protein intakes for those seeking weight loss are suggested to be higher mostly to prevent muscle loss – not necessarily growth.

Can both occur at the same time?

So herein lies the difficulty – building muscle and losing fat can sometimes be in conflict with one another. This is particularly the case for a well-trained athlete or someone in a heavy training period or competition phase. This is why most athletes are recommended to pursue body composition changes in off-season training. Additionally, fat and muscle are not gained or loss entirely irrespective of one another. In other words, gaining muscle means you will also gain some fat, and losing fat means you will also lose some muscle. This is why body composition assessment can be so important to understanding exactly what has shifted rather than focusing purely on weight.

For a sedentary individual new to resistance training, a modest caloric deficit may contribute to fat loss while also allowing muscle building. And in fact, reduced calorie plans do necessitate a higher protein intake to ensure muscle protein synthesis. Beyond body composition impacts, chronic participation in heavy training periods without adequate energy intake can contribute things like reduced bone mineral density, overtraining syndrome, and reduced immune system response.

So consider your goals carefully – if gaining muscle is the priority then focus on adequate protein and carbohydrate intake to support workouts; if fat loss is the priority then ensure protein intake is adequate to prevent muscle loss and workout intensity is manageable given reduced energy intake.

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