The Scientific Way to Lose Weight Without Dieting

Kasey McClurg, Endurance Sport Center @EndureSport

How often do you hear that diet and exercise are the key to weight loss? But how many people still struggle to lose weight or keep it off? Yeah, a cubic shit-ton is about accurate. For this discussion, we are going to explore how you can lose weight without changing a thing in your diet. That’s right. A nutritionist is telling you to LEAVE YOUR DIET ALONE for the time being. We all know it’s not realistic to uproot and change your entire life habits at one time, so we are going to focus on the one physical thing you can do to right away to start losing weight.

In the health and fitness world, we often hear a slight caloric deficit is a key to weight loss because the body will look to its energy storage in adipose tissue, thus fat will be lost.2 Let’s break down how fat is lost, not to be confused by weight, a difference which will be covered in the near future. Simply put, the body needs fuel to convert to energy to make life process happen. This comes in the form of nutrients and vitamins you get from your food, which get broken down into its base components to fuel your cells. Of these food fuels, your body (generally) will use energy from carbohydrates first, followed by fats, and finally (and hopefully never) proteins. Your body stores this food energy in places like your muscles and liver, but they can only hold so much. So you eat too many carbs and fats, your body has to store it somewhere else. So it stores it in adipose tissues, AKA, it makes body fat (insert gasp).2

So now we want to lose body fat for our various reasons. In order to accomplish this, we have to get our body to burn calories, right? But not all calories are the same. If we are wanting our body to burn stored fat, which is composed of both extra carbs and extra fats as we explained. So you have to burn through enough stored energy in your liver and muscles to get around to the reserves in our adipose tissue.2

Sidenote: I find it helps to think of body “fat” and energy potential. You aren’t necessarily burning fat, you are using fuel. I digress…

So it makes sense that, in order to “firm up,” we need to use the stored energy we already have stored in our adipose tissue. If you follow this logic, you are probably seeing where this is going. By restricting caloric intake through dieting, we aren’t burning through the stored energy. We are just slowing the storage process. Sure, you can go more extreme and not eat enough food for your body to function, forcing it to metabolize the stored energy to survive and you’ll lose weight. And you won’t get your micronutrients to properly function. And you have a strong chance of developing an eating disorder. And you’ll be uncomfortable and unhappy and grouch. And you’ll eventually quit, wasting all your time on unsustainable habits and being unhappy for no reason. But if we introduce exercise into the equation, now we are starting to burn off fuel.

Think of it this way: your body is a car, your fuel is food, and your body fat is the gas tank. Your car sits there and never moves. Every day, you put a little more fuel into the gas tank. But it never moves, so the gas tank gets topped off very quickly. But you keep putting more gas in and it spills out and you have to put a bucket under the spout to keep it from spilling everywhere. You’re tired of buckets of gasoline around everywhere and you received a nasty notice from the local fire department warning you of the improper storage of your hazardous materials. Here are our scenarios:

1. You decide to reduce the amount of gas you put in the tank every day, so now it overfills at a slower rate. This equals less buckets of gas. But you are so used to buying gasoline that you get sad when you can’t hoard it. You can stop putting gas in the tank, but this doesn’t make the other buckets go away and doesn’t solve your problem. You can try to siphon out the gas, but you are going to inhale some nastiness and probably get gas in your mouth. It just isn’t safe. This is what happens when you calorie restrict alone.

2. You don’t want to stop with your gas-purchasing obsession, so decide you can start to drive your car. You can still put the gas you wanted in the tank every day and supplement the rest it with your buckets of reserved gas. As long as you keep the car moving, you don’t have to change anything else. This is how you start to make changes through exercise alone. It’s a lot more efficient than the aforementioned deprivations.

3. You finally get inspired and decide to change your habits, so you drive your car every day and put less fuel in the tank everyday, topping it off with the reserve fuel. Whuddaya know, you go through that extra gas really quickly now and can finally get the fire department off your case. This is how exercise and nutritional modifications can help us burn off excess energy or adipose fat.

Now we get to the science, yay!

It is important to note while caloric restriction may result in initial weight loss, the popular ideology of restricting and balancing calories is highly ineffective in long-term weight maintenance among healthy and obese individuals.4 Long-term studies (6-12 months) have been performed showing caloric restrictions and low-calorie diets decrease total daily energy expenditures3, catabolize skeletal and myocardial muscle, and significantly decrease the body's physical work capacity.4

Why does this matter?

A 12 month study4 concluded caloric restriction alone significantly decreased thigh muscle mass and knee flexion strength, significantly reduced VO2max (aerobic capacity), and ultimately reduced participant's overall physical work capacity. These results were echoed in another study,3 which showed caloric restriction and low calorie diets reduced participants' total daily energy expenditures over time. Both studies introduced exercise as weight loss measures, which showed significant improvements in muscle tone, strength, and cardiovascular capacity when used in conjunction with caloric restriction.3,4 We already assumed this would happen based on common knowledge. However, the study4 went a step further and maintained the same caloric intake while increasing exercise-only weight loss. This measure showed similar weight loss results as the calorie-restricted group, but showed a significant increase in muscle mass and both absolute and relative VO2max. The calorie-restricted group showed significant decreases in these areas.

What does this mean?

Given change management methodologies, we should only make one change at a time for sustainable results.1 When a person is considering weight loss or maintenance plans, we should take and exercise-first approach before considering caloric restriction. Introducing even a 12.5% increase in total daily expenditures through exercise3 will provide a weight loss and maintenance foundation without jeopardizing the person’s cardiovascular capacity and energy level. Only then should we introduce caloric restriction conversations. We should not suggest dietary changes alone for this type of person, as we could be setting them up for a more sedentary lifestyle long-term.

Does this explain why many people who seek weight loss coaching regress and even gain more weight after weight loss programs?

I know what I think, but you be the judge.


1) Bregman, P. (2009, October 6). To change effectively, change just one thing. Harvard Business Review.

2) Denniston, K. J., Topping, J. J., Caret, R. L., & Quirk Dorr, D. R. (2017). General, organic, and biochemistry (9th ed.). Chapter 17. Lipids and their functions in biochemical systems, pp. 597-632. McGraw Hill Education.

3) Redman, L.M., Heilbronn, L.K., Martin, C.K., de Jonge, L., Williamson, D.A., et al. (2009) Metabolic and Behavioral Compensations in Response to Caloric Restriction: Implications for the Maintenance of Weight Loss. PLOS ONE 4(2): e4377.

4) Weiss, E. P., Racette, S. B., Villareal, D. T., Fontana, L., Karen Steger-May, Schechtman, K. B., Klein, S., Ehsani, A. A., Holloszy, J. O., Washington University School of Medicine, CALERIE Group, & Washington University School of Medicine, CALERIE Group. (2007). Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss. Journal of Applied Physiology, 102(2), 634-640. DOI https://10.1152/japplphysiol.00853.2006

Disclosure: The statements made in the above article are based on scientific evidence and references are provided. These statements are intended to be educational and general in nature. Each person is unique, and results and health care needs will vary. While the strategies included generally rank low on the risk versus harm scale, you should consult with a professional if you have questions, chronic health conditions, or before engaging in long-term lifestyle changes. Endurance Sport Center and Kasey Co, LLC, are not liable for the application of this information outside of our direct coaching programs.

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