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  • Writer's pictureRyan Allen

Macronutrient balance and carbohydrate intake

I’m often asked–especially as someone who has type 1 diabetes and wears a continuous glucose monitor (CGM) to see my blood sugar 24/7–about how I view carbohydrate intake, and macronutrient breakdown in general in my diet. The funny thing is, the more and more I learn about nutrition, the less and less it seems to matter to me what someone actually eats. Yet, it is certainly up there with the topics any doctor will get asked about the most.

Now, I know it may seem like a controversial statement that I am decreasingly valuing the constitution of one’s diet, as nutrition and various diets tend to stir up some of the strongest opinions in the field of health. However, I want to emphasize a couple things. The first is that I am not devaluing it entirely; I definitely think there are things that can derail long-term health if included in one’s diet with any real frequency. The obvious example that comes to mind is the inclusion of ultra-processed foods, or various compounds foreign to the body for which we have no good mechanism of metabolism or disposal. The main concern with many of these sorts of things is some kind of toxicity, or even carcinogenic component. This is a very different kind of toxicity from, say, the effects of sugar intake on metabolism, which is a far more complicated and even debated concept.

The second point I want to emphasize is that it does matter what each person is consuming, but likely just at the individual level. In other words, it matters that someone is eating a diet that consists of what works for them. This then brings to me to my key point when it comes to nutrition: in my view, every person’s nutritional regimen should, above all, be a means of obtaining sufficient protein and sufficient fiber through a minimal caloric intake to reach those goals. This is not to say that these are the only important aspects of one’s diet, but for me, they certainly should be approaching the top of the list. And again, this is still ideally done through a real, whole foods diet to prevent possible toxicities of various manufactured foods, aid in digestion, provide appropriate quantities of essential micronutrients, etc.

With all of that said, how do carbohydrates fit in this framework? Well, you have three macronutrients: protein, carbohydrates, and fats. Protein is a unique macronutrient, in that it is mainly used to form much of the structural and functional components of every cell in our bodies. This is why it is so important to prioritize. Regardless, while it will of course constitute calories, as a fuel source, it is pretty inefficient to metabolize. So, once we’ve reached our protein goal, we fill in the rest of our allotment of calories with our main fuel sources: carbohydrates and fats. Now, I’ve written quite a bit on carbohydrate and fat metabolism, mainly in the context of fueling for athletic endeavors depending on performance goals. As far as the balance goes between carbohydrate and fat intake, I am becoming less convinced that it really matters.

For me, I have always done better on a higher fat, lower carbohydrate diet. I always just feel more satiated and sustained throughout the day with long-lasting healthy fats, and often just get hungrier when consuming carbs. There is likely something to this with the insulin effect of major carbohydrate intake, where the more carbs you eat, the more insulin you secrete, the hungrier you get due to proposed downstream insulin signaling mechanisms. It has long been shown in studies that hyperinsulinemia (high levels of insulin in the bloodstream) correlates with increased appetite, although to my knowledge this is still a little debated mechanistically. This and other theories around insulin as a major culprit in obesity are often employed by low-carb advocates, and still seem potentially substantive in my opinion. That said, data seems to regularly show that “low-carb, high-fat” and “low-fat, high-carb” diets perform similarly on the vast majority of relevant health metrics, when holding calories equal between the two diets.

It is very worth noting that carbohydrate constitution matters, primarily in the game of blood sugar control. Preventing major blood sugar spikes should be a high priority nutritionally, and there are a few ways to prevent that. The most important is avoidance of high-sugar drinks: soda, juice, sports drinks, energy drinks, etc. I often describe these as “straight injections of sugar into the bloodstream.” This is because they quickly make their way through the gut and get absorbed with their liquid form and lack of fiber. You can think of fiber as something that delays absorption, and facilitates appropriate gut health through this and feeding the microbiome. Thus, to prevent blood sugar spikes, we want as high of a fiber-to-sugar or fiber-to-total carbohydrate ratio as possible (recall that any carbohydrate intake is almost akin to sugar intake; carbs get rapidly converted to glucose in the body and raise blood sugar). You may see various foods that refer to “net carbs,” which is based on this principle. Net carbs are equal to total carbs minus any dietary fiber or unmetabolized carbohydrate sweeteners, since these two carbohydrate forms virtually do not contribute to blood sugar response (or even blunt it). So, for example, an average banana has 27g of total carbohydrate, 3g of which are fiber, and of course no artificial sweeteners. It would have 24g of “net carbs” contributing to one’s blood sugar response. I think there is something to minimizing one’s total net carb burden, although I think this concept matters significantly more for high-calorie processed foods, or refined carbohydrates like pastas or white bread, than natural foods like fruits.

In addition to the sugar-fiber (or total carb-fiber) balance, the final thing I think about with carbohydrate intake is the kind of sugar being consumed. The main form of sugar present in our bodies that we use as fuel is glucose. However, other forms of sugar exist, the simplest of which is fructose. Our bodies do have pathways for metabolizing fructose, so we are evolved to consume it. The problem is, we were evolved to use it for rapid fuel storage; in other words, we used it to fatten up as much as possible for harsh winters and periods of starvation, much like a hibernating bear. In modernity, we have fructose in abundance in the form of added sugars (which are made of sucrose, a combination of glucose and fructose), and are consuming it in excess. I won’t go entirely into the fine details and harms of fructose metabolism now as I have previously, but suffice it to say I view added sugars as something to definitely restrict. Fructose is also present in fruits, however most fruits have minimal amounts relative to processed foods sweetened with added sugars. Additionally, the fruits often come with large amounts of fiber and water to help balance out any possible burden of excess sugar absorption. The only fruits that could pose issues are things like grapes or especially any dried fruits, as these have very high concentrations of sugar and much of the fiber stripped out. If possible, I would opt for fruits higher in fiber and lower in sugar/fructose, like berries.


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