The Science of Insulin: How Insulin Affects Your Weight and Body Composition

The Science of Insulin: How Insulin Affects Your Weight and Body Composition

The Science of Insulin: How Insulin Affects Your Weight and Body CompositionIs controlling your weight more than just calories in-calories out? There’s little doubt that the diet you eat impacts the levels of hormones that affect your weight and body composition. One such hormone is insulin. Insulin is a hormone produced by your pancreas that is essential for life. People who have type 1 diabetes don’t produce insulin because the cells in the pancreas that produce them have been destroyed. As a result, they’ll die unless treated with insulin. This shows how important insulin is for sustaining life. It also plays an important role in controlling body weight, appetite and, when you work out, muscle growth.

Function of Insulin: What Insulin Does

Insulin plays a major role in energy metabolism and storage. Without insulin, glucose can’t enter cells. As you know, glucose is an important source of energy, especially for the brain. Without insulin to help ferry glucose into cells, they would literally starve from lack of fuel.

Insulin also plays a role in the storage of lipids and the synthesis of proteins. Insulin helps to move amino acids into muscle cells where they can be used for muscle growth and repair in response to resistance training. That’s why insulin is a bodybuilder’s best friend because it boosts protein synthesis but it also can be their worst enemy, as you’ll see.

How Insulin Makes You Fat

Insulin is an energy storage hormone. When there’s excess glucose, in the presence of insulin, muscle cells and liver cells take up glucose and store it as glycogen, so you’ll have adequate energy stores for your next workout – but there’s a limit to how much glycogen your muscle and liver cells can hold. When there’s too much, glucose is converted to fatty acids and then into triglycerides, the storage form of fat. It does this under the hormonal influence of insulin. At the same time, insulin puts the brakes on fat breakdown. That’s why some people refer to it as a fat storage hormone. Unlike glycogen storage, your body has an unlimited ability to store fat.

The real problem arises when cells become resistant to the effects of insulin. If you eat a diet of rapidly-absorbed carbohydrates that lack fiber, they’re absorbed very rapidly, causing blood sugar levels to spike. Since glucose is a signal that causes insulin release, this rapid rise in blood sugar causes your pancreas to pump out more insulin. Over time, when your cells are exposed to higher levels of insulin, the receptors on them that bind insulin become less responsive to it. This is a condition called insulin resistance. To compensate, your pancreas pumps out even more insulin. These higher levels of insulin create ideal conditions for fat storage because insulin boosts the conversion of glucose to fatty acids, which go on to be stored as fat in an insulin-rich environment. Insulin also puts the brakes on fat breakdown.

There’s another way insulin promotes fat storage. It activates an enzyme called lipoprotein lipase. Lipoprotein lipase is found on cells that line capillaries in your muscles, fat tissue and the heart. What does it do?

Fats or triglycerides ride around in your bloodstream on lipoproteins. Lipoprotein lipase, activated by insulin, breaks down these triglycerides into fatty acids so they can be stored inside cells when your body doesn’t need energy. Insulin also blocks the action of another hormone called hormone-sensitive lipase that has the opposite effects – it breaks down fat. As you can see, insulin does everything in its power to help your body store energy and hold onto fat.

Insulin Resistance is the Real Problem

When insulin becomes a problem is when your cells become resistant to it. When your pancreas has to keep pumping out more and more of it to get glucose into cells, you store more fat. Plus, it puts stress on your pancreas to produce more insulin. Eventually, your pancreas may “burn out” and be unable to meet your body’s demands for insulin. That’s when your blood sugars start to rise and you cross over into type 2 diabetes. Fat storage, type 2 diabetes and an increased risk for heart disease – that’s the end result of insulin resistance.

The key to getting the benefits of insulin without the negative effects is to maximize the ability of your cells to respond to insulin so your pancreas doesn’t have to overproduce it. Here are some tips for helping your cells respond better to insulin:


Exercise, both aerobic and resistance training, increases insulin sensitivity. Cells are also able to take up glucose in the absence of insulin during physical exercise. High-intensity exercise seems to improve insulin sensitivity more than low-intensity workouts.

Reduce or Eliminate Processed Foods

Processed foods and sugar-sweetened beverages, like soft drinks and fruit juice, are rapidly absorbed, causing insulin spikes that contribute to insulin resistance. In contrast, fiber-rich foods are absorbed more slowly and require your pancreas to produce less insulin. Choose more whole foods and foods rich in fiber.

Get Enough Sleep

Don’t skimp on sleep. It’s essential for maintaining insulin sensitivity. Research shows that insulin sensitivity declines after even one night of inadequate sleep. How much do you need? Don’t get less than seven hours of sleep a night and aim for eight.

 Tap Into the Power of Cinnamon

Cinnamon contains an ingredient that improves insulin sensitivity. You can get the benefits from as little as a half teaspoon of cinnamon a day. Add it to your breakfast cereal in the morning or to a cup of coffee.

The Best Time for Simple Carbs is After a Workout

When you do eat rapidly absorbed carbs, the best time to do it is right after a workout since insulin sensitivity is highest at this time. Combine it with protein after a resistance training workout and you’ll speed the amino acids from the protein into muscle cells to boost muscle growth and repair.

 The Bottom Line?

Insulin is a hormone vital to life and important for energy storage and muscle growth. The key to getting the benefits is to avoid insulin resistance through diet and exercise.



Int J Sports Med. 2000 Jan;21(1):1-12.

Journal of Applied Physiology July 1, 2005 vol. 99 no. 1 338-343.

Science Daily. “One Sleepless Night Can Induce Insulin Resistance in Healthy People”

United States Department of Agriculture. “Cinnamon Extracts “Boost Insulin Sensitivity”


4 thoughts on “The Science of Insulin: How Insulin Affects Your Weight and Body Composition

  1. Also, be wary of the “5-6 small meals per day” rule. This can also cause insulin resistance. Spiking insulin several times per day.
    I learned this the hard way, since my diet has always been impeccably clean, and I have always worked out.

  2. Struggling with this. I’m lean and exercise and eat clean, but I am insulin resistant. I’ve been following the 5 to 6 meals a day. Suggestions?

  3. I seem to be insulin resistant but I do exercise regularly and eat well except for the very few occasions on weekends. Thanks for sharing this article, very helpful.

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