skip to Main Content
Weight Gain 101: Where Did This Extra Weight Come From?

Weight Gain 101: Where Did This Extra Weight Come From?

Now that Thanksgiving and Christmas are over, and the new year has begun, it’s time to attack that resolution to change your body. Whether you’re on a mission to gain weight, or you’re looking to shed unwanted pounds, it’s a good idea to understand the basics of why we gain weight. If you’ve been struggling to gain or lose weight for a while, you may need to seek the advice of a medical professional. Your doctor may want to check your insulin, thyroid, or other relevant levels.

What is a Calorie, and Why Should I Care?

In terms of nutrition, a calorie is a unit of measure that indicates how much energy a food contains. According to Anthony Komaroff, MD, “Calories are units representing the ability of food to be converted by the body into energy. All food contains calories, and we need a certain amount of calories each day.[1]

The energy in food comes from a variety of sources including protein, carbohydrates and fat[2]. Together protein, carbohydrates and fat are called macronutrients, the basic components of healthy diets. Each macronutrient contains a certain amount of energy, or calories. But not all calories are created equally.

Here’s the breakdown for each:

  • 1 gram of protein contains approximately 4 calories[3]
  • 1 gram of carbs contains approximately 4 calories[3]
  • 1 gram of fat contains approximately 9 calories[3]

There are a several reasons you may be putting on weight. We’ve addressed a few of the more prevalent factors below.

You’re Eating and Drinking More Calories Than You’re Burning

There are 3,500 calories in 1 pound of body fat. When you eat more calories than you burn, you create caloric excess.

Example: A 45-year-old man weighs 150 pounds. He eats 2,500 calories a day for 7 days in a row. Through exercise he burns about 425 calories per day, and his body’s natural calorie burning mechanism (resting metabolic rate or RMR) contributes about 1,575[4]* calories per day, for a total of 2,000 calories a day. (*Calculated using the Mifflin-St. Jeor Equation.)

Despite his considerable movement, he creates an excess of 500 calories every day over a 7-day period, for a total of 3,500 calories. He accumulated 3,500 calories more than he burned off, which means he just gained 1 pound. This is one way to gain weight.

Your Carb Intake Is Too High

Carbs are your body’s primary fuel source. When you eat or drink carbs, your body converts them to sugar (called glucose). This is the case for all carbs – simple or complex, fast or slow, bad or good. As glucose levels in your blood increase, your pancreas produces insulin, which allows your cells to absorb the glucose for immediate energy, or store excess glucose in your muscles and liver as glycogen. This energy is used by your muscles, cells and brain. This is how your body regulates higher blood sugar levels[5].

Once your muscles and liver are full of glycogen, the excess glucose is stored as fat for use at a later time. Unfortunately for many, later never seems to come.

“I Could Eat Anything I Wanted 20 Years Ago”

Your muscles play a key role in your body’s ability to burn fat while at rest. This is called your resting metabolic rate (RMR).

Unfortunately, if we aren’t proactive in maintaining muscle mass, our bodies tend to lose up to 10% of existing muscle mass per decade starting around age 30.

The gradual loss in muscle mass means less natural burning ability due to the lower RMR.

Let’s take another look at the 45-year-old man in the example above, assuming the same weight, calorie intake and calories burned each day through exercise. That same man 20 years earlier (at age 25) would naturally burn about 1,668 calories per day[4].

Based on this information, it would have taken approximately 1½ days longer for this man to gain the same 1 pound 20 years prior. Projected out for 365 days, the man would gain approximately 52 pounds over the course of 1 year at age 45 versus 42 pounds over that same year at age 25.

Now that you understand how the body gains weight, be sure to take a look at the best ways to shed those unwanted pounds.


[1] Harvard T.H. Chan School of Public Health. (n.d.). Understanding empty calories. Retrieved February 1, 2020, from

[2] Szalay, J. (2015, November 14). What Are Calories? Retrieved from

[3] USDA National Agricultural Library. (n.d.). How many calories are in one gram of fat, carbohydrate, or protein? Retrieved February 1, 2020, from

[4] Kelly, M. P. (n.d.). Resting Metabolic Rate: Best Ways to Measure It-And Raise It, Too. Retrieved January 25, 2020, from

[5] Harvard T.H. Chan School of Public Health. (2016, July 25). Carbohydrates and Blood Sugar. Retrieved from

Back To Top