Biochemistry of Calories and Weight Loss


Okay.  Let’s start with the basics.  If you understand the why and how of weight loss and weight gain, then losing weight is an easy concept that is very difficult to maintain.  Weight loss is not as easy as just pushing back from the table or not filling the feed bag.  You will need to understand the macronutrients (fat, protein, carbohydrates, and possibly alcohol) and have a good estimate of how many calories you should eat.

Calories are a measurement of the energy in food.  Just like a watt of electricity will light a bulb or turn a motor, a calorie will help you build parts of your body or can be used to move your body.  You need them to operate and to continue to live.  A calorie to your body is like gasoline for your car.

macronutrients and calories

Figure 1:  Macronutrients and Calories

Where do we get calories?  The main sources for most people are carbohydrates, fats, and proteins.  There are other sources, such as alcohol.  I chose to include alcohol to illustrate how dense it is in calories.  One calorie is equal to 1000 kcal, but we call them Calories (note the capital).  Most folks just drop the capital letter.  You can click on the above image to see it larger.

Now that you understand the calories.  Lets talk about weight gain and weight loss.  Our bodies need energy to move, repair, and perform many other processes.  We get them in the form of calories from our food.  So let me explain the basics of weight gain and weight loss.  If you understand this, you will understand what you need to do to lose weight.

Energy Balance

Figure 2:  Energy Balance

The Energy Balance is the key to weight loss and weight gain (Figure 2 above. Click for a larger image.). If you understand the basics, it will make dieting easier. The image of the balance above is like the teeter-totter we played on in the schoolyard as a kid. The good news is there are two kids on the side we need to be heavier. The bad news is it is hard to resist overeating, so the left side of the teeter-totter always has the potential to have a heavier kid.

Now, let’s talk about weight loss and weight gain, and calorie imbalance. I am going to simplify the right side of the balance by calling it just “calories burned.”

Weight Gain

Figure 3:  Weight Gain

The above image (Figure 3) depicts what happens when you eat more calories than you burn. You will gain weight, and your waistline will expand.

Weight Loss

Figure 4: Weight Loss

Figure 4 depicts the balance for weight loss. If you burn more calories than you eat, you will lose weight.

No Weight Change

Figure 5: No Weight Change

Figure 5 depicts the balance for no weight gain or loss. If you balance the calories than you eat with the same as you burn, you will maintain the same weight. 

So how much of each macronutrient should I eat, and where do I get them?

I usually go with a 50/25/25/0% rule, with 50% of calories from carbohydrates, 25% from protein, 25% from fat, and 0% from alcohol.  I do not always make this ratio, but I try.  Remember that alcohol is an empty calorie, so if you have it, you need to eat less of something else or exercise more.

Macronutrients Ratio

Figure 5:  Macronutrients Ratio

The bottom line: Weight loss and proper nutrition depend on moderation and good food choices.  I hope this article helps you lose weight.  If you understand the sources and density of each source in calories, it is easier to make smart choices. Good luck with making smart food choices.  

Print Friendly, PDF & Email

About the Author

I am a family physician who has served in the US Army. In 2016, I found myself overweight, out of shape, and unhealthy, so I made a change to improve my health. This blog is the chronology of my path to better health and what I have learned along the way.

Be the first to comment on "Biochemistry of Calories and Weight Loss"

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.