Insulin. If you were to understand only one thing about your body, this may be it. Insulin is a hormone produced in the pancreas that functions to regulate carbohydrate and fat metabolism in your body. As you consume sugar-laden and carbohydrate rich foods, the pancreas releases a proportional amount of insulin to regulate glucose (blood sugar) levels. When glucose levels are too high, it becomes toxic for your body. Diabetes mellitus is the commonly known disease where the body can no longer adequately regulate glucose. Type 2 Diabetes, which makes up about 90% of all cases, is a metabolic condition comorbid with obesity. In a healthy individual with a good metabolism, insulin functions by reacting with insulin receptors located on the surface of the liver and muscle tissues to store excess glucose as glycogen. If glucose levels fall too low, the glycogen stores are accessed to provide your body with the needed sugar. This is an important homeostatic system as your brain needs a constant supply of glucose to function. The brain actually consumes 25% of your body’s total glucose. If your brain stops working, you stop working. Accordingly glucose is the prioritized energy substrate of the body. Its regulation and supply are of the utmost importance to the body.
Looking at this from an evolutionary perspective and considering sugary and starchy foods were harder to come by in the prehistoric eras, it makes sense that the body has adapted to ensure a constant and consistent supply of glucose. If your glucose runs low, you tap into your glycogen stores. If your glycogen stores run low, you tap into your fat stores. You can think of glycogen stores as your bank account and fat cells as your savings account. You don’t keep as much money in your bank account but it's pretty easy to access when you need it. In savings, you keep a significant amount more of money but it's harder to access, maybe tied up by investments. Continuing with this analogy, the body looks at glucose like money because it’s great biological value. That’s why the body so willingly stores away extra glucose. The other macronutrients, fat and protein, have complex mechanism for metabolizing into glucose because it is the prioritized energy substrate of the body. However, what happens when carbohydrates become the most common macronutrient? When there is an over abundance of starch-laden foods that spike blood sugar in combination with a culture that abhors dietary fat?
Enter the 21st century. Actually, enter the 20th century, but who’s counting. People have steadily been getting fatter since the Center for Disease Control (CDC) started keeping track in the early 1980s. The most recent government- funded survey reported that approximately 69% of adults are overweight or obese, with more than 78 million adult Americans considered obese (NHANES, 2009-2010). For the last 20+ years people have been told to avoid dietary fat because it was thought of to be associated with heart disease. Consumer marketing caught on with this trend and brought fat free and low-fat foods to the forefront of supermarket shelves everywhere. Coincidently, grain is considered the basis of a "healthy" diet and was the foundation of the U.S. Department of Agriculture’s food pyramid which recommended 6-11 servings from the bread, cereal, rice and pasta group. Fat is placed at the top of the pyramid with no recommended daily serving. Similarly, the World Health Organization food guidelines recommends 55-75% of the diet to be made of carbohydrates. This seems to be in contrast to Stanford’s A TO Z Weight Loss study which I briefly mentioned in my previous post. Stanford’s study has been the longest and largest comparative study using randomized trials on diet to date. It showed the Atkins diet to have the greatest effect on weight loss and the best benefits on improving cholesterol and blood pressure, both important markers of heart disease. Atkins is not a semi-starvation type diet like some of the other more common diets in the study. Atkins works by initially restricting carbohydrates and then slowly redirecting people toward more healthy carbohydrate sources (low glycemic carbs) as they reach their weight loss goals. A carbohydrate restricted diet seems to be in stark contrast to the recommendations of the USDA, and WHO which recommended a diet biased toward starchy carbs.
One of the reasons why Atkins is so effective is because it works by resetting the metabolism. It decreases insulin resistance and enables the body to fully utilize the calories instead of storing them as excess fat. Atkins is a completely different paradigm then other diets. The total amount of calories consumed is a non issue. Eat until you are full, just mind the carbs.
To review: Carbohydrate rich foods spike blood sugar which stimulates insulin. The insulin interacts with insulin receptors on your muscle and liver tissues to store the extra sugar for possible later use (glycogen synthesis) as well as prevent toxicity.
A diet that is high in starchy carbohydrates and sugar stimulates insulin often, which eventually can lead to insulin resistance. The receptors stop reacting to insulin and the next stage of metabolism takes over. The extra glucose is stored as fat. Normally this happens only after glycogen stores have been filled. The normal metabolic pathway works something like this: Too much glucose? Replenish glycogen storage in the muscles and liver and store the rest as fat. Too little glucose? Utilize the glycogen stores and work on metabolizing fat.
In the prediabetic state of insulin resistance this is no longer true; the extra glucose gets shuttled straight into the fat cells. This may also have secondary effects on hunger and energy since the calories are not fully utilized by the muscles but are appropriated to the fat cells, making the individual feel like they have low energy and are hungry all the time. American science writer Gary Taubes described this in his book Why We Get Fat and What to Do About It, when he compares obese individuals to the malnourished or starving. This seems crazy but makes sense in a way because the metabolism literately shuts down from all the sugar and starch in the diet. The fat cells start consuming an abnormal amount of calories and leave less energy for the rest of the body. In this sense fat people are literately starving. The recipe to combat this is simple. Make better choices about the foods you eat and worry less about the amount. If your diet consists primarily of high glycemic carbohydrates and foods containing lots of sugar, you will likely start to develop some of these metabolic issues. The research suggests that we should get more of our calories from fat and protein and start consuming carbohydrates that can be utilized by the body instead of just turning straight into glucose. Check out the glycemic index for more info on healthy carbohydrate choices.
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