What Makes An Exercise Muscle Building or Body Slimming?

Author - Stephen Griffith C.S.C.S. Pn1

Woman - “My thighs are too big and I want them to be slimmer. What exercises are good for slimming a person’s legs?”

Man  - “My upper body is well developed, and it makes it look like I have chicken legs. What’s a good exercise for growing my thighs?”

I answered both questions with squats.


Squats are an exercise that works a lot of muscle, has a strong metabolic effect, and builds a strong lower body. They’re an essential part any balanced workout program.

This begs the question -How can an exercise be both slimming and bulking?

In both examples, the same exercise can produce very different aesthetic results. It can give a man his herculean figure or give a woman her slim toned physique.

In fact, I’ve even given the same strength training program to two different people. One got larger, and the other got slimmer. How?

What determines the difference is nutrition.

Muscle is great to have. It provides shape and definition to the body. It burns calories, provides strength, manages hormones like insulin, and is essential to well being.

Because muscle burns calories and requires a surplus of protein, it is expensive to have.

A person who wants to build muscle and get bigger will be required to eat a surplus of protein and calories.

This is why you often see bodybuilders eating so much, so often.

In contrast, a person who wants to get slimmer will look to eat at a maintenance level or in a deficit.

For these people, the exercises give the body a reason to maintain the muscle they have but the lack of calories means that their body won’t have the surplus it needs to build new muscle.

Together the training maintains the muscle and allows the weight they lose to be from fat and not muscle. As they lose fat - they get leaner.

I once trained a model. She needed to tone up before a series of shoots so I created a program that would do that. The program consisted of several weight training exercises - the same I might use for the guy who wants to bulk up. As a model, she was concerned the exercises would bulk her up which for her would mean she’d be out of business. However, I assured her that even with the strength training she wouldn’t be able to bulk up as long as we managed her diet.


It’s the same reason Kate Upton can train like a beast but doesn’t turn into a bulky bodybuilder.


One final note on why muscle is also slimming -

It’s denser than fat which means pound for pound it takes up less space.

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Below is an example of a woman before and after photo. In both, she weighs the same weight but shows radically different physiques. The reason is that her muscular physique in the 2nd photo takes up less space than the fat in the 1st.



To build muscle requires consistent hard training combined with a surplus of protein and calories. This is how an exercise can bulk a person up.

To slim down, you can use the same exercises but in the absence of a surplus of protein and calories, the body will instead maintain the muscle it has and burn excess fat. Resulting in a toned and slimmer physique.  

Lastly, pound for pound muscle just takes up less space.

Train hard, don’t be afraid of muscle, and tailor your diet to your goals.

With this goal of education and building independence, I started Fitness Made Clear. I encourage anyone reading to subscribe (at the bottom of the page) and share to support the cause and spread the simple, informative, and actionable information on this site to others.

Stephen GriffithComment