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Do carbohydrates make you fat?

Carbohydrates are sugars or starches. They are organic molecules that are composed of carbon, hydrogen, and oxygen atoms, they are the most abundant food source and a key form of energy for most organisms. Our body, however, does not require carbohydrate to survive.

The family of carbohydrates (carbs) includes both simple and complex sugars — glucose and fructose are examples of simple sugars, and starch, glycogen, and cellulose are examples of complex sugars. The complex sugars are also called polysaccharides and are made of multiple monosaccharide molecules.

Polysaccharides serve as energy storage (for example starch and glycogen) and as structural components (for example chitin in insects and cellulose in plants).

Carbohydrates are everywhere, and in most cases can easily create addiction. Some obvious examples include bread, pasta, potatoes and baked goods. However, you can also find carbs in your salad dressing, ketchup, fried foods, milk, yogurt, ice-cream, fruits, most low-fat processed food and much more.

When you consume carbohydrates they are broken down into simple, soluble sugars that can be transported across the intestinal wall into the circulatory system to be transported throughout the body.

Carbohydrate digestion actually begins with saliva in the mouth, continues in the duodenum with the action of pancreatic amylase, and ends with monosaccharides being absorbed in the small intestine.

When you eat excessive amounts of carbohydrate, they will be converted to fat and stored in a process called lipogenesis. A diet that contains excessively high carb intake, even just for a few days, is likely to make you fat.

If, at the same time, you lower your fat intake then this will dramatically reduce the amount of carbs that are converted to body fat. Most people, however, prefer to consume foods that are both high in carbs and high in fat.

Low-fat food generally does not taste as good, and will not satisfy you, so you will end up eating more processed “junk” food — which really is not real food at all.

The second way that carbs interact with fat is when consuming carbohydrates causes a spike in blood glucose and insulin levels. Insulin is a hormone that mediates glucose metabolism. When insulin is high, it switches the body from fat burning mode into carbohydrate burning mode.

This allows carbohydrates (and glycogen) to be burnt at a greater rate, but directly reduces the ability of fat to be lost, so more fat can go into body fat stores (as it is not needed, because glucose from glycogen is being used in place of it).

Refined carbohydrates also have an adverse affect on blood glucose and insulin levels. These carbs have gone through a manufacturing process that breaks down the complexity of their natural chains, allowing them to be digested quickly, and rapidly increasing serum blood glucose levels.

When a notable increase in blood glucose occurs the acute hyperglycemia is commonly referred to as a “glucose spike”. The body, in response, releases insulin to try to return it back to a state of homeostasis.

The increased insulin levels then promote a higher rate of fat storage, and the insulin allows the entry of glucose into fat cells by converting it into triglycerides in the liver.

The fuel that our body needs for energy expenditure is supplied by protein, carbohydrate and fat. This fuel can be supplied by the diet, or can come from our body’s energy stores.

We have a limited capacity to store carbohydrate as glycogen (a typical adult male can store approximately 500g of glycogen, predominantly in muscle and liver) and conversion of carbohydrate to fat is energetically expensive.

Fat, however, can be stored almost without limit (largely in adipose tissue), and much more efficiently.

So what is the solution? It would seem that the best approach is to eat real foods (ideally in their natural state, i.e. with no label on them!), to consume good quality whole-food fats, and to not consume more than 30-40 grams carbs in any one meal.

An example of that quantity of carbs would be one medium sweet potato, or half a cup of rice, or two apples. If you are consuming more than this with each meal then you might want to look more closely at what you are eating — especially if you are insulin resistant, diagnosed with type 2 diabetes, or pre-diabetic.


Ayda Ersoy is a nutrition and fitness director at The Diet Doc Hawaii. She can be reached at, or
(808) 276-6892
Source: The Garden Island

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