Evlo Fitness/Education/Types of Exercise/The science of exercise and fat loss
Shannon Ritchey
Dark Mode

The science of exercise and fat loss

Let me start by saying that I do not focus on weight-loss with my clients. Study after study has shown that “trying to lose weight” by dieting doesn’t work long term. But understanding your body’s mechanisms to lose fat is important in order to implement a healthy routine. Understanding exercise science will help reduce unhealthy norms like over-exercising to burn calories and look fit.

This post will include education on fat loss, how steady-state cardio isn’t beneficial for fat loss, and how and why to gain muscle with high intensity exercise.

Re-examining fat

Fat storage is a sign of good health – that the metabolic processes are operating correctly, and the body is thriving. We all know that excess fat places additional stress on the system and can cause health issues. However, not ENOUGH fat can also cause health issues and metabolic dysfunction. So striving to achieve a body that has very little fat is not a healthy goal. 

Everyone will carry a varying amount of body fat, depending on that individual’s genetic code. This gene is called the “ob gene” and affects our appetite. When our body fat falls below the “ideal” level determined by this gene, our appetite will increase to build back the appropriate fat stores to keep our systems functioning and healthy. On the other hand, when fat levels exceed the ideal fat percentage, appetite will decline to encourage fat levels to stabilize. (Of course, I’m over-simplifying the influences of appetite, but just to demonstrate that our bodies have different genetic preferences to fat stores. There is no ubiquitous fat percentage that can be applied to every person). (1) 


Steady-state cardio isn’t efficient for weight loss.

Steady-state activity is a cardiovascular exercise that can be sustained for an extended period of time (45 min-1 hour) like jogging, walking, or an aerobics class. This does not place a high-intensity demand on the muscles, which is why it can be carried out for so long. You are using a small percentage of your slow-twitch fibers over and over. If you are exclusively doing steady-state cardio, you will lose muscle mass, which will decrease your basal metabolic rate even more. Interestingly, as you participate in more steady-state cardio, your body gets more efficient at it, and you burn fewer calories than you did initially. This is why a runner’s “endurance” doesn’t necessarily transition to endurance on a bike. Their body simply got more efficient at the motor patterns required for running.

Gaining muscle as we age is key to maintaining a healthy body.

With aging, we lose muscle, a phenomenon called sarcopenia. This will cause your basal metabolic rate to decline (how many calories your body burns to keep you alive). This is why you eat the same amount that you ate in your 20’s, and you’re slowly putting on weight. 

Muscle burns more calories than any tissue in your body. In other words, it requires lots of energy to keep you alive, around 50-100 calories per pound of muscle per day. So if you gain 5 pounds of muscle, you will be burning an additional 500 calories/day, even if you don’t work out.

This is why the key is to improve your basal metabolic rate by gaining more muscle. As you increase your muscle mass, you will have the ability to participate in more vigorous activities without compromising your joints, and you will continually improve your basal metabolic rate. This upward spiral will allow you more freedom with food because your body will burn more calories at rest. Say goodbye to counting calories forever.

When you cut calories, but you aren’t strength training, your body will not only decrease fat, but also decrease muscle, bone, and connective tissue in that caloric deficit. This will lower your basal metabolic rate (because you’ve lost muscle tissue), and you will have to “diet” your entire life to maintain a certain weight. 

However, when you are strength training, you are placing high demand on your system to lay down more muscle, bone, connective tissue, and neural tissue, so the body’s weight loss will come exclusively from fat. If you control your nutrition by eating unprocessed foods and control insulin levels (see a nutrition specialist for information on this), you can approach a healthy body fat with lots of protective muscle. 

So how do we gain muscle without getting hurt?

So the idea is to introduce high-intensity training that is of short duration. This introduces enough stress for the body to stimulate regrowth, but not so much that your system is overwhelmed, becomes inflamed, and sets you back. If you’re injured, you won’t be able to exercise and can lose ground.

People hear “high intensity” and form a mental picture of someone sprinting and doing burpees. This scares people away who have experienced injuries or are novices. Although this is one way to perform high-intensity exercise, it comes with unnecessary risks. There is a more productive way that will yield the same benefits, but with less risk. 

The safest, most productive way to do HIIT

The best resistance training program is one of high intensity but low force. In other words, choose exercises that will efficiently develop muscle and are low risk of injuring joint structures. Several main principles should be applied to this: 

1. Train your muscles

I know this seems obvious, but I think we often get caught up in what the movement looks like and less about what muscles we are training, how we are putting forces through joints, and if those joints can tolerate said forces. Focus on the muscle groups you are training, and stabilize the rest of your body for the safest and best results.

This will allow your body to focus fully on producing the strongest possible output while minimizing stress through adjacent joints. This is why a leg press is more effective than a squat at gaining strength in the legs. 

2. SLOW. 

People think of HIIT as velocity-based and fast. This is not necessarily the most productive way to do HIIT. Doing speed-based exercises isn’t “bad,” but it will increase the amount of force through the joints and also apply momentum to the movements. This combination means that your joints are taking most of the stress, not your muscles (I think this is why there is such a prevalence of injuries in many HIIT-based workouts). 

Here’s how you ramp up the intensity without speed: try taking 10 seconds for each rep. If you are lifting heavy enough weight, you will be dripping in sweat by the end of that set. This will feel very intense, but without less negative stresses through your joints. (Disclaimer: you have to choose stable exercises! Try this with a leg press, a machine chest press, or a machine row. HARD and EFFECTIVE.)

3. Perform few repetitions

This means adding heavy weight (and going slow) where few repetitions (anywhere from 4-20 reps) lead to muscle failure or fatigue. This is more effective for gaining muscle and will be safer on your joints (if you choose safe exercises, as stated above).

4. Give yourself 1-4 days in between HIIT workouts

When you exercise a muscle to fatigue, it takes anywhere from 1-4 days for that tissue to recover. So if you’re exercising the same muscle to fatigue more than two times a week, you could be over-stressing your system, leading to overtraining syndrome. This can cause symptoms like fatigue, joint dysfunction, irritability, and weight gain.

5. Keep the workouts short 

HIIT workouts don’t need to be longer than 20 minutes. Tack on a warm-up and cool down, and you’re done in 30 minutes or less.  

People are hesitant to do short workouts because they think of exercise as something that burns a lot of calories. But the long-term calorie burn is not coming from the amount of time you’re exercising, but the tissue you’re building during that workout. People who exercise intensely for long periods and/or too many days a week while cutting calories introduce too many stressors on their system. This spikes cortisol levels, which creates an environment where the body will be hesitant to let go of fat. When your body perceives a threat, the result is a slowed metabolism, preservation of body fat, and of course, injuries.