We’ve all grown up equating sugar to energy, but new research suggests our bodies are engineered to run on fat…
I recently attended a fascinating series of meetings in Baltimore, MD accompanied by the top physiology and weight loss specialists in the country. Although I’d long known sugar was dangerous and advised limiting all carbs to 50-100gm per day, going into the meeting I’d assumed we needed some. Specifically, I thought our brain cells required glucose because that’s what I learned from biochemistry books, physiology books, and other medical texts.
During the meeting, however, I became convinced by the abundance of newer lab and clinical data showing that brain cells, and the vast majority of other cells in the body, actually prefer a product of fat metabolism, called ketone bodies. The power plants of the cell that burn oxygen to produce energy in the form of ATP, called mitochondria, function poorly in the presence of another chemical, called malonyl-coA, which comes from the breakdown of glucose. Forcing mitochondria to deal with malonyl-coA overwhelmes their ability to control the high-energy electrons used in the making of ATP, and the result is a release of free radicals. Free radicals can cause DNA mutations as well as enzymatic destruction.
A minority of cell types actually do require glucose, specifically a few types of cells in the liver and cells without mitochondria (e.g., red blood cells). All other cells work perfectly well burning fat and special kinds of fat-breakdown molecules called ketone bodies. According to world-renowned metabolism expert Dr. Mary Vernon, we need 30 gm (2 Tbsp) of glucose per day to keep those cells that prefer glucose running properly. That small amount can readily be supplied by the conversion of protein to glucose in a metabolic process carried out through a cooperation between the liver and kidney, called gluconeogenesis.
What about Adrenal “Burn-Out”?
Somebody got the idea circulating that low-carb diets might cause adrenal “burn out,” and a few readers have asked about this. I’ve looked everywhere and I can’t find any data supporting the theory. I do find a physiologically plausible mechanism by which carb consumption may cause adrenal gland problems. Take a look at the diagram I’ve adapted here (below) from a lecture presented by Dr. Jeff Volek. It illustrates the mechanism by which high carb diets produce energy swings.
It’s important to consider that, if you have a metabolism that’s been running on glucose for decades, your metabolism is not in a healthy state and therefore will need some time to realign itself with the input of proper nutrition. You’ll need to give your body some time to adapt to the new fat-burning state. A whole new set of enzymes will need to be re-manufactured, which can take a few weeks to accomplish. For those with metabolisms in serious trouble, I typically advise going low-carb one meal at a time giving each mealime two weeks (see http://TRIMProgram.com for more on how I help my patients change habits.)
Bottom line: All the latest science contradicts the assertion that we need carbs—any carbs—in our diets. This isn’t to suggest that everyone needs to remove carbohydrates entirely from their diets. Indeed, there may be some as-yet undiscovered benefit to dietary sugar. Today’s article is not meant to suggest that we’d all be better off with zero carbs in our diet. It is, however, meant to point out that very few of our cells need dietary sugars for energy, and therefore the old idea that we need to include carbs in our diets or we’ll feel tired all the time, is running on empty.
ADDENDUM: Thanks to Paul Jaminet, Matt Stone, Cheeseslave and others, there has been a much-needed awareness-raising of the fact that we can overdo every good thing. Since originally posting, I’ve added the following caveat:
I believe that just as we enjoy a change of pace from time to time, so does our metabolism. There may be benefits from consuming enough carb to kick you out of ketosis (50-120 gm per day) on occasion. I suspect our ancestors enjoyed seasonal fruit binges from time to time, for example, and a rare (emphasise RARE) infusion of simple carbohydrate may flood your body with a variety of different sugar molecules in ways that aid fertility, and support tissues that require sugar molecules for structural purposes (like tear and mucuous production by the eyes and digestive system). Just remember, whatever as-yet unexplained benefit carb-flooding may offer, it may also temporarily stall weight loss .