Carbs & Insulin Explained In Plain English
Have you noticed that there’s a tremendous amount of confusion associated with nutrition in general, and carbohydrates in particular? Let’s clear things up.
What Is A Carb?
First of all a carb is not a TYPE of food, it is a PART of food. There are three substances that are classified as carbohydrates.
- Sugar. This can be sugar from fruit, honey, or a box labeled “Dixie Crystals.” While there are different types of sugar that we eat, they are all considered “simple” carbohydrates.
- Starch. This is a long chain of sugar molecules. Once we eat it, the body breaks it down into sugar. However, because it is “complex,” the process takes longer.
- Fiber. Fiber is also considered a complex carbohydrate, but unlike sugar and starch, it is not absorbed by the body. Instead, it helps with digestion (along with a lot of other things).
As you can see, the terms “simple” and “complex” are almost entirely unhelpful. The practical difference is between fiber (which passes through the body), and sugar/starch (which are absorbed by the body).
What Does The Body Do With Sugar/Starch?
During digestion, sugar/starch is broken down into its simplest possible form. The scientific term for this is a “monosaccharide.” The most common monosaccharide is called glucose. The bloodstream carries glucose throughout the body, so that it can be absorbed by other cells. While glucose is in the bloodstream, it is frequently referred to as “blood sugar.”
In a healthy person, the amount of glucose in the blood (AKA “blood sugar level”) is kept fairly stable. The body does this by using a hormone called insulin to regulate how much glucose is in the blood, and how much is absorbed by cells in the muscles and organs.
All You Need To Know About Insulin
Insulin is produced by the pancreas, and tells cells to absorb glucose. If the cells respond effectively, we call this being insulin sensitive. If the cells do not respond quickly, the pancreas has to produce more insulin to get the message through. We call this insulin resistance.
Generally speaking, insulin sensitivity is a good thing. Your pancreas doesn’t have to work as hard, and the cells in your muscles and liver can absorb glucose readily, either to use as fuel or to store for later in a form called glycogen. This is desirable, because glucose that isn’t used as fuel or stored as glycogen is turned into fat.
The fact that excess glucose is stored as fat is the key to the low-carb diet argument. While excess calories from protein or dietary fat will also be stored as body fat, carbohydrates seems to cause a greater fat gain. This is partially because some types of sugar may block the body from using fat as fuel, and also because eating carbohydrates doesn’t seem to stimulate the appetite-suppressing hormone leptin as effectively as fat and protein do.
How Low-Carb Diets Work
If you consume fewer carbohydrates than your body needs for fuel, your pancreas will produce a hormone called glucagon. Glucagon is basically the opposite of insulin. It releases the glucose stored as glycogen back into the bloodstream. As your glycogen stores are depleted, glucagon also starts breaking down adipose tissue (fat) into glycerol and free fatty acids through a process called lipolysis. Almost every cell in the body (except the brain and red blood cells) can use free fatty acids for fuel, so this is quite effective. Lipolysis is what people are talking about when they refer to “burning fat.”
Related to lipolysis, the body has a mechanism for synthesizing glucose called gluconeogenesis. This is the creation of glucose from glycerol (released from fat), lactate (a by-product of the muscles, especially when exercising), and amino acids, such as those found in protein. The rationale for low-carb diets is that, since synthesizing glucose from these alternate sources is far less efficient than simply using glucose directly from carbohydrates, the body has to work harder to do it. This uses up more energy, which means that the body is burning more calories just to use food as fuel. Also, if you’re not consuming more sugar/starch than your body can use, there’s no excess glucose to be stored as fat.
Notably, gluconeogenesis is the source of the myth that the body will “break down muscle” without a constant supply of food. Gluconeogenesis WILL break down skeletal muscle into its component amino acids, but not until after 24 to 48 hours without eating. As long as nutrition is otherwise adequate, simply skipping breakfast, or even only eating one meal a day will not result in loss of muscle tissue.
Speaking of skipping breakfast; since the body doesn’t start to run out of glycogen until around 12 hours after eating carbohydrates, lipolysis doesn’t really get rolling until around that time. This is the rationale for intermittent fasting: simply by waiting longer to eat, your body will burn fat for energy.
There’s Always A Catch
Low-carb diets sound pretty compelling, and there’s certainly a lot to be said for not consuming EXCESS carbs. What “excess” means depends on your age and activity level, but the Institute of Medicine’s Food and Nutrition Board says that 130 grams per day is the bare minimum. In contrast to that, the Ketogenic diet recommends limiting total daily carbs to around 20 grams.
There are two main issues with restricting carbs so severely. One is that you’re likely to wind up with deficiencies of nutrients like fiber and vitamin D, as well as excesses of other things like ammonia and nitrogen. The other is that it’s so difficult to eat that way, almost nobody can stick with it! Imagine never again having bread, pasta, pizza, cookies, or a glass of juice. In fact, the compliance rate for ultra-low-carb diets is so low that most professional dieticians and nutritionists don’t recommend it unless there’s a compelling medical reason (such as controlling epilepsy).
A Sensible Strategy
Even though low-carb diets can be difficult, and cause a lot of arguments among scientists and nutritionists, there are a few points on which everyone agrees.
- Don’t eat too much of anything. Excess calories are stored as fat. It’s that simple. The more closely you can align what you eat to what your body needs, the more effectively your body will work. Apps like MyFitnessPal can help you calculate and track this.
- Eat less sugar. Everybody needs a chocolate chip cookie now and then. But nobody needs to drink Coke or eat donuts on a regular basis. Minimizing sugary drinks and processed snack foods is critical for anyone trying to achieve or maintain a healthy level of body fat. Also, making small changes like swapping out white bread in favor of whole-grain bread can have a very positive impact.
- Get active. Not only does exercise stimulate your muscles to burn fat, it increases insulin sensitivity and causes a cascade of other positive hormonal effects throughout the body, including improving mood and sleep. If any pill did what exercise can do, everybody would be taking it. You don’t need a gym membership or equipment either; check out DareBee for a wide variety of free, schedule-friendly, at-home workouts programs.
- Be patient. Lifestyle changes take time. Don’t fall into the “New Year’s resolution” trap of trying to change everything all at once, only to burn out and give up in a few weeks. Instead, take the advice of Charles Duhigg’s book, “The Power of Habit” — focus on one positive change at a time, and stick with it until it becomes a habit. Then, add another one, and so on.
Hopefully, understanding how carbohydrates work and are processed by the body will help you evaluate the claims made by proponents of various trendy diets. Ultimately, it comes down to this: if it doesn’t make sense, or you wouldn’t be able to do it forever, leave it alone!