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How Insulin, Carbs, and Sugar Impact Weight Loss

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Losing weight is not as simple as calories in vs. calories out.

Carbs, insulin, and high fructose corn syrup (HFCS) have an ENORMOUS IMPACT on weight loss and body fat.

Don’t get me wrong–calories do matter–but weight loss and fat storage go far beyond a formula. If weight-loss only came down to calories in vs. calories out, would America really be 35% obese? I doubt it.

If you’ve been “dieting,” but haven’t seen the weight loss to show for it, fixing your diet to manipulate insulin levels and control blood sugar is most likely your golden ticket to a lean, phenomenal body.


The Science Behind Carbs and Insulin, and How They Control Weight

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Whenever you eat carbs they’re broken down into simple carbohydrates (aka sugar), which directly impacts blood sugar levels in the body.

**Remember: carbs = blood sugar fluctuations



Carbs are graded on an index known as the Glycemic Index or GI. The GI measures how quickly carbs raise blood sugar levels in the body. Foods with a HIGH GI (on a scale up to 100) digest extremely quickly and create rapid a blood sugar response–what I’ll refer to as a “spike.” Pure sugar–or glucose–is is rated at 100.

  • Refined carbs (white bread, white rice, corn flakes, etc.) have a very high GI. This is because most of the nutrients and fiber are stripped out for flavor.
  • Complex carbs (100% whole wheat bread, brown rice, oatmeal, vegetables, etc.) have a low/medium GI and a manageable impact on blood sugar.
  • has an accurate list of GI values for common foods.

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A carbs’ impact on blood sugar is ALWAYS reduced when eaten with protein, healthy fats, fiber, or some combo of all 3. This is know as the Glycemic Load or GL. GL is basically the re-indexed GI for an entire meal.

As a rough example: a baked potato on its own has a GI of 85, which is classified as extremely high. If you eat the baked potato with chicken and beans–two EXTREMELY low GI foods–the GL of the entire meal will be much lower, somewhere sub 50.



Insulin is a hormone, created by the pancreas, that the body releases to help reduce blood sugar levels (from eating too many carbs and sugar!).

Insulin’s major function is to tell the body when to store nutrients–one of which is fat. Insulin is essentially a gatekeeper, which opens up the body’s cells and directs them to store fat and/or release fat into the blood. 

When the body senses that blood sugar is elevated–again, from eating carbs and sugar–it calls on insulin to open the flood gates and stuff blood sugar away into cells.

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Muscles are the body’s largest storehouse of blood glucose–otherwise known as glycogen. Think of muscles as the body’s gas tanks. When there’s an overflow of glucose circulating through the bloodstream insulin shuttles that glucose into the muscle cells until they’re full. After a beastly workout muscle glycogen stores are depleted–that’s why it’s absolutely CRITICAL to eat post-workout.



When muscle cells fill up they signal to the body that no more glucose can be transported in, which creates a glucose backup and signals for insulin to rise.

Insulin + full muscle cells is a BAD, BAD situation.

When insulin levels rise any blood sugar left in the bloodstream WILL be stuffed away somewhere. Unfortunately, if you’re lazy and don’t burn off any calories/stored calories, well…all of that blood sugar shuttles straight into fat cells (aka adipose tissue).

Although it’s not a hard and fast rule, in general, elevated insulin levels = fat storage. Sugar–I’m staring directly at you.

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When insulin spikes over, and over, and over again it creates a condition known as insulin resistance. Insulin resistance (aka Metabolic Syndrome or prediabetes) is exactly that–the body’s inability to effectively use insulin and control blood sugar levels, which leads directly to develop Type-II Diabetes.

A few of the ways to control insulin and prevent diabetes include:

  • Eat slow digesting, low-GI, complex carbs
  • Avoid all sugar and refined carbs
  • ALWAYS eat carbs with slower-digesting protein and healthy fats



The one time it’s advantageous to eat high GI carbs (fast digesting) or sugar is after an intense workout. Intense workouts burn a TON of calories and fully deplete the glycogen stored in muscle cells. Exercise essentially empties muscle fuel cells–precisely the same way a car runs out of gas after a long drive.

It’s critical to refill those tanks as soon as possible to facilitate new growth and prevent muscle breakdown/loss (aka catabolism). Eating sugar and high GI carbs–combined with protein directly post-workout–spikes insulin and quickly shuttles glucose, protein, and other nutrients to depleted muscles as quickly as possible. This kickstarts the growth and recovery process and ensures that no muscle is ever used up as fuel.



To lose fat insulin levels have to drop. The enzyme that removes body fat from fat cells is called Hormone Sensitive Lipase or HSL. HSL is sensitive to insulin levels. It functions when insulin levels are low, and is suppressed when insulin levels are high. If insulin is too high, even if you’re in a caloric deficit, HSL will not be signaled to function and you’ll be physically incapable of losing body fat! All you’ll do is burn off muscle tissue and maybe gain a little bit of fat…not a  good state to be in.

To Recap: Carb & sugar intake -> blood sugar spike -> increased insulin levels -> fill glycogen stores in muscle cells -> all excess STORES AS BODY FAT! 


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Bryan DiSanto

Founder & Editor-in-Chief at Lean It UP
ELLO ELLO I'm Bryan DiSanto. I'm the Founder & Editor-in-Chief of Lean It UP, a CPT/CSN/Fitness Coach, Chef trained at Le Cordon Bleu – Paris, NYU graduate, ex-fat kid, and all-around fitness junkie.

I also contribute to Men's Health Magazine.

When I'm not working on my abs (or somebody else’s), whipping up avocado roses and avocado toast, or running a Tough Mudder, I'm probably yelling at a Carolina Panthers game somewhere.

Come be friends with me on Instagram (@BRYDISANTO) & Snapchat (BRYDISANTO).
Bryan DiSanto
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