The Truth About Carbs

There is a lot of hype today about low-carb diets, including lower fruit intake.  It’s a pity, because carbohydrates should actually make up the highest percentage of your macronutrient intake (protein and fat are the other two), and fruit is full of vitamins and nutrients the body needs.  Let’s break down the importance of carbohydrates and look at which carbohydrates are best for your body.

Carbohydrates are compounds containing carbon, hydrogen, and oxygen and are generally classified as sugars (simple), starches (complex), and fiber.  Monosaccharides (single sugar unit – many connect to make starches and glycogen) include glucose (blood sugar), fructose (fruit sugar), and galactose.  Disaccharides (two sugar units) include sucrose (common sugar), lactose (milk sugar), and maltose. Polysaccharides are long chains of monosaccharide units linked together and found in foods that contain starch and fiber.  Carbohydrates are a primary source of energy for all body functions and muscular exertion.  Carbohydrates also help regulate the digestion and utilization of protein and fat.

Carbohydrate availability is vital for maximal performance (sport and workout).  Here’s how the uses breakdown:

  • High-intensity, short-duration activity (anaerobic), muscular demand for energy is dependent on muscle glycogen.
  • Endurance exercise (aerobic) performed at moderate moderate intensity, muscle glycogen provides about 50% of energy needs.
  • High-intensity aerobic exercise, glycogen stores yield all of the energy needs.

Essentially, the limiting factor for exercise performance is carbohydrate availability.  One’s diet is recommended to include 2.7 to 4.5 g/lb.  This means, an adult should be consuming 45 to 65% of total caloric intake from carbohydrates.  Complex carbohydrates (think whole grains, fresh fruits and vegetables) should constitute the majority of calories because of their nutrient dense nature.

The facts about carbohydrates and weight gain are as follows:  data from the Third National Health and Nutrition Examination survey summarizing patterns for the years 1988 through 1991 show that percentage of calories consumed from fat has dropped, from 36% to 34% of total energy intake; however, when total fat intake is measured, versus simply the percentage contributed, data shows that fat intake has remained constant for the past several years.  Furthermore, this data may not accurately display fat intake in America, as many people underreport fat consumption owing to it’s negative health connotations.  The Third National Health and Nutrition Examination Survey also shows an increase in total energy intake.  This would explain the relationship of excessive energy intake leading to increased fat stores.  It is worth noting that data on Americans’ food intake in the early 1900s indicates the percentage of carbohydrates consumed as energy was higher and fat intake lower than it is today, without the prevalence of obesity experienced today.  There are two primary variables for this rise in obesity: an increased energy intake and a reduction in energy expenditure (as stated in an earlier post, estimates show that more than 75% of the American adult population does not partake, on a daily basis, in 30 minutes of low-to-moderate physical activity).  The point?  American’s increasing obesity problem is not a direct result of carbohydrate intake, rather it is an energy imbalance.  Listen to your body, and respect it’s needs.

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