Taking Control of Your Dietary Composition Part 12

Last installment, I explored the controversy regarding the role of carbohydrates in a healthy diet and how this debate is polarized into two camps. Carbohydrate proponents warn that a low-carb approach compromises health in exchange for weight loss only attributable to depleted glycogen stores and associated water loss with a potential for muscle wasting to boot. Conversely, anti-carb advocates argue that high carbohydrate intake destroys your ability to metabolize fat. The take-home message was that like many polarized debates, both extreme viewpoints miss the mark although each is based on legitimate facts because many of those facts are taken out of context.

Low-carb critics speak of the potential for ketosis, which can, indeed, be harmful and even fatal. Consequently, understanding this altered metabolic state is a first step for discovering the truth. When carbohydrate intake is dramatically restricted and glycogen stores become depleted, fat is relied upon as fuel to a greater extent. Now, this might seem like beneficial if you’re trying to lose body fat, but the problem is that under these circumstances, free fatty acids cannot be completely degraded. The end result is that energy-containing acidic bodies called ketones accumulate in the blood and when this “ketosis” causes the blood to become excessively acidic (e.g., in patients with uncontrolled diabetes), severe health complications can arise. So, warnings from the pro-carb camp are not unfounded. However, extreme ketosis (e.g., “diabetic ketosis”) is generally not present when ketosis is induced by reasonable dietary manipulation. In fact, the body actually adapts to such “dietary ketosis” in that circulating ketones serve as an alternative fuel source for body tissues including the brain. So, score one for the anti-carb camp because at least over the short term, dietary ketosis does not appear to warrant significant health concerns.

In addition to ketones, individuals following a low-carb regimen also metabolize amino acids (i.e., the building blocks of protein and, therefore, structural components of body tissues including muscle) to a greater extent. This can be problematic because unlike fat and carbohydrates, amino acids are not stored in the body. Consequently, there is a potential for muscle breakdown when ketosis is in effect. However, the classic example would be during fasting when insufficient caloric intake is also present (i.e., “starvation ketosis”) and this contrasts a reasonably-structured ketogenic diet where the energetic void created by carbohydrate removal is at least partially compensated for by increased protein intake. For example, while athletes might need as much as 1.8 grams, the recommended dietary allowance for protein is only 0.8 grams per pound of bodyweight, which means that it’s not difficult to satisfy normal protein turnover when a balanced diet is consumed. Consequently, skewing intake from carbs in favor of protein and fat when following the low-carb approach would likely provide enough of a surplus of amino acids to cover whatever increased amounts would be used for energetic requirements. So, once again, dire warnings from the pro-carb camp are likely overstated. 

Risks of the low-carb diet might be exaggerated, but in and of itself, this doesn’t mean you should purge pasta from your plate because unless there are significant benefits, it’s difficult to reconcile why a more balanced approach still wouldn’t be your best bet. So, the next step is to assess the claims of low-carb proponents. The major one is that high carbohydrate intake decreases the use of fat as fuel and this is absolutely the case because of hormonal fluctuations that allow the body to rely upon what is most readily available. However, this does not mean that it’s impossible to lose body fat if you ingest a high percentage of energy in the form of carbohydrates because it is overall energy balance that ultimately dictates how fat stores are affected. So, if the energy you require to maintain your current fat stores (i.e., your caloric maintenance level) is 2,000 kilocalories per day, any caloric intake above that will make you deposit additional fat even if you’re eating a minimum amount of carbohydrates which promotes maximum fat usage. Conversely, fat stores will be accessed if you consistently ingest less than your caloric maintenance level even if you do so with a diet rich in carbohydrates that shifts your metabolic state away from fat burn.   

The bottom line is that the low-carb approach is not advantageous for fat loss on a calorie-for-calorie basis. However, Johnstone et al. found that subjects eating ad libium chose to ingest less food when following a low-carb compared to balanced diet when both comprised approximately 270 kilocalories per pound of food offered. This meant that subjects wound up ingesting less energy when substituting fat and protein for carbs and the likely reason was that ketone bodies exert an anorexic effect. So, it appears that the major advantage of adopting a low-carb approach is that it tricks the dieter into craving less food, which brings fat loss as long as the energetic density of the food being consumed remains relatively constant. On the other hand, it seems reasonable to suggest that those who prefer to chose the amount of energy they ingest in a calculated manner would be better served by a more balanced approach because they will already know the appropriate amount of food/energy to consume. And this is particularly the case for athletes and those who opt to prioritize fat loss via maximizing energy expenditure because maximum glycogen stores are necessary to exercise at a high intensity.    

This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.




Go back