How Carbohydrates Make You Fat

Carbohydrates are consumed by boatloads in our country. Nearly all traditional diets include plenty of carb sources, even sometimes on the expense of protein foods. Many of our great strong men of past had thrived on these diets. Also, the physically hyperactive lifestyle during the preceding times makes consumption of super high carbs a necessity for performance.

But now the times have changed dramatically. The sedentary lifestyle is rampant, even in the rural. But we’re still eating more or less the same. The result is the widespread epidemic of lifestyle-related diseases, like obesity, diabetes, high BP, and cholesterol etc. Most people are quick to chop off fats in their diets as a measure to restore wellness because fat, as we know, is the most caloric dense. Even doctors recommend cutting fats as a means to limit cholesterol. But still it is not helping the overweight to cut fat. Obese are getting obeser.

The Carbs Quandary

Many people believe that carbs are just your body’s preferential fuel source which do not get deposited into fat stores. A few nutritionists and physicians also profess that lipogenesis (fat production) through carb metabolism is too inefficient, and body doesn’t prefer to convert carbs into fat, so carbs are pretty safe. But in actuality, plenty of fatties seem to defy this logic. How do they do it? Let’s understand.

There are two direct pathways through which carbs get turned into fats in your body.

1. De Novo Lipogenesis

De novo lipogenesis means to produce fat from the sources other than fat, like carbs. This process transforms the glucose from carbs directly into the lipids which are then stored in the form of body fat. Indeed this process is pretty inefficient, and a high degree of fat can’t be produced by this process. But when excessive amount of carbs are present in a hypercaloric diet over a period of time, this conversion becomes quite possible (Acheson, McDevitt, Minehira). This condition is your free ticket for obesity and type II diabetes.

2. Insulin Action

Insulin is a storage hormone secreted by pancreas in response to the blood sugar elevated by ingestion of food, particularly carbs. The job of insulin is to clear out excessive sugars from the blood stream and get them stored elsewhere, your liver, muscles and fat cells. Liver and muscles have a limited storage capacity but your fat cells can really swell and grow to accommodate extra energy.

In the presence of insulin your body can’t mobilize stored fat since it is in the storage mode, and thus burns carbs preferentially. This stops the lipolysis (fat burning) to various degrees in proportion to insulin spike. Macro nutrient partitioning makes use of this physiological process to your benefit by eliminating carbs at certain times to preferentially burn fat. Now, when dietary fat is also present alongside this insulin spike, it directly moves to the fat cells for storage instead of burning.

Lesson Learned

Carbs can either be your friend or foe. Use them wisely and judiciously. If you use them as a means to fuel your physical activity, carbs will be your best friend. They will provide you energy and preserve lean body mass. But if you overfeed carbs to yourself, they’ll turn you into an obese, diabetic rotund man in extreme despair.

References
  • Acheson KJ, et al Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man . Am J Clin Nutr. (1988).
  • McDevitt RM, et al De novo lipogenesis during controlled overfeeding with sucrose or glucose in lean and obese women . Am J Clin Nutr. (2001).
  • Minehira K, et al Effect of carbohydrate overfeeding on whole body and adipose tissue metabolism in humans . Obes Res. (2003).

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