- Sheri Colberg, PhD
(Why I) Count Calories, Not Just Carbs
Whenever someone gets diagnosed with type 1 diabetes (T1D) nowadays, the first thing that an educator or dietitian tries to teach them is how to count carbohydrates (carbs). Although I have been living with T1D now for almost half a century, I have to admit that I don’t count carbs. Not only that, but I personally don’t think carb counting works very well! But I also don't avoid them.
The whole point of counting carbs is to try to balance the dose of mealtime insulin with carb intake to avoid post-meal spikes in blood glucose or hypoglycemia later on. Carbs are digested and fully absorbed within one to two hours after you eat them, and they undeniably have the most direct and dramatic impact on blood glucose levels. All carbs get broken down into simple sugars (glucose, fructose, or galactose), and the latter two (fructose and galactose) can easily be converted into glucose, which is the primary simple sugar in blood.
The problem I see with carb counting is two-fold: first, not all carbs are equal with regard to their glycemic effect (how much they raise blood glucose and how quickly) and; second, carbs are not the only component of food that can affect your blood glucose levels. Foods with a higher glycemic index (GI, found on glycemicindex.com) cause more rapid spikes in blood glucose after you eat them, but it also depends on the total amount of carbs in what you eat (the GL, or glycemic load). For example, carrots have a high GI, but their GL is fairly low, meaning that you would have to eat a lot of them to raise your blood glucose much. Pasta, on the other hand, is digested more slowly and has a moderate GI, but the load can be tremendous and enough to raise your blood glucose slowly for hours afterwards.
In the first 18 years when I had diabetes without a blood glucose meter, I was taught to make every meal a balanced one (carbs, protein, and fat) and only have a certain number of servings in each category. I naturally gravitated away from eating fewer highly processed carb foods (made with white flour and white sugar) and more towards foods that didn’t make me feel crappy after eating them because they had a lower GI. To this day, I eat a lot of high-fiber, low-carb veggies (green ones like lettuce, green beans, and broccoli), only moderate amounts of starchy veggies (like corn, peas, and potatoes), and very few white carbs with a high GI. Honestly, if I were to count carbs and dose with mealtime (bolus) insulin for them, I would end up low after every meal and high later on due to how slowly my meals cause my blood glucose to rise!
The second part of the issue relates to the fact that intake of protein and fat can also impact insulin needs and blood glucose. Excess protein is turned into glucose and raises blood glucose within three to four hours after you eat it. This works well when you’re trying to prevent later-onset hypoglycemia, but not so well when you don’t have the insulin in your body to cover the rise in blood glucose naturally. Although fats are not directly converted into glucose, during rest your body will use fat over glucose, and the fats released from food make you insulin resistant for that reason. Recently, research done at the Joslin Diabetes Center showed that when people eat the same exact amount of carbs in two dinners but differing amounts of fat and calories, they have to take more insulin to cover the meal with more fat (1). I could have told them that just from personal experience!
In 2015, a systematic review (2) came up with similar findings: All studies examining the effect of fat, protein, and GI indicated that these dietary factors modify your blood glucose after meals. Late postprandial hyperglycemia was the predominant effect of dietary fat; however, in some studies, blood glucose was lower in the first 2-3 hours, possibly due to a slower emptying form the stomach. These studies also reported that high-fat/protein meals require more insulin than lower-fat/protein meals with identical carbohydrate content. Such findings point to the need for research focused on the development of new insulin dosing algorithms based on meal composition rather than on carbohydrate content alone.
Another related problem arises from the types of insulin that people use as mealtime insulin. Back in the “dark ages” of diabetes care, I started out using what was called “Regular” insulin, which had a slow onset and lasted for many hours after the meal. Actually, I wish I still used R insulin as it would likely cover the mixed meals I eat better than the rapid-acting insulins on the market now (I've heard you can still buy R without a prescription, but haven't tried getting any). The rapid-acting ones available now (Humalog, Novolog, Apidra, and inhaled Exubera) only really last for a couple of hours, and they’re really ineffective at covering the rise in blood glucose arising from fat and protein digestion and absorption long after the carbs are gone.
My personal strategy to deal with the way rapid-acting insulins work is to take higher levels of basal insulin during the day to help cover my protein and fat intake. I also check my blood glucose an hour or so after eating every meal and correct with extra insulin then based on my blood glucose level and my expected response to whatever remaining calories in the food I ate (mostly coming from low GI carbs, protein, and fat).
So, what should you do if you choose not to count carbs? Learn as much as you can about what you’re eating. Read food labels to find out how many grams of carbs, protein, and fat are in your foods. Record everything you eat and drink (and do) for at least a month and see what your unique response is to foods you eat on a regular basis. (I did this for at least a decade after I finally had a blood glucose meter to learn my individual response to everything.) It may also help to actually measure out what you’re eating with measuring cups or a kitchen scale until you get a better idea of what portions you’re taking in as well. Most Americans these days have portion distortion and eat way more than they think. Most of all, just consider more than the carbs that you’re consuming when it comes to managing your postmeal spikes effectively.
(1) Wolpert HA, Atakov-Castillo A, Smith SA, Steil GM: Dietary fat acutely increases glucose concentrations and insulin requirements in patients with type 1 diabetes: implications for carbohydrate-based bolus dose calculation and intensive diabetes management. Diabetes Care 2013;36:810-816
(2) Bell KJ, Smart CE, Steil GM, Brand-Miller JC, King B, Wolpert HA: Impact of fat, protein, and glycemic index on postprandial glucose control in type 1 diabetes: Implications for intensive diabetes management in the continuous glucose monitoring era. Diabetes care 2015;38:1008-1015