I read an interesting article on the NYT Well blog: Eating Fat, Staying Lean that contained some data from a recent Johns Hopkins study.
Kerry Stewart, director of clinical and research and exercise physiology at Johns Hopkins University School of Medicine is publishing initial findings of a long term study on diet and exercise. Study participants in the low-carb/high-fat group lost 10 pounds in an average of 45 days while it took the low-fat calorie restricted group an average of 70 days.
It’s interesting to note that in the study both groups reduced their caloric intake by about 750 calories. I’ve found if I don’t eat enough my weight loss stalls out and my metabolism (or desire to exercise) takes a nose dive. I find that restricting calories by following the calories in calories out theory of weight control leads to inferior results. It’s next to impossible to maintain any sort of exercise program without consuming enough food.
The real weight loss occurs not because of restricted calories but from the reduced insulin levels. In my post Carbs = Fatness I quoted some research that supports this. Insulin is a storage hormone, when levels are pushed higher by ingesting sugars the body stores energy as fat. To release energy or fat from your fat cells your insulin levels must be low enough for other hormones to be produced and break down fatty acids.
Fat Metabolism Blocked by Insulin
Fat metabolism can not occur when when your body is full of glucose (carbs) and thus insulin.
The image for this post is a simple illustration of insulin metabolism. When we ingest carbohydrates they are broken down into glucose and absorbed in the upper part of the small intestine. Glucose then enters the blood stream an our pancreas produces insulin which stores the glucose in our muscles as glycogen or in our fat cells as a glycerol and three fatty acids or a triglyceride. Another effect if insulin is that it lowers fat utilization through the prevention of fatty acid oxidation. Insulin prevents your from using fat as fuel.
Fat People are Starving?
Here’s another interesting point. If we are even a little bit insulin resistant, and most fat people are, then our pancreas will produce extra insulin to get our blood glucose in check. Remember, insulin stores glucose in our cells; a good thing in muscles and bad in fat cells. Well when all of the glucose has been shuttled out of the blood stream by excess insulin into our fat cells the other cells in the body start signaling for energy. However, our elevated insulin levels prevent lipolysis, or burning fat for energy, so our cells signal some more and we end up being hungry. This is a cyclical process; our fat cells soak up all the energy we ingest as food and because of elevated insulin levels there is an energy deficit for our other cells. So, you guessed it, we eat and then the process begins again.
A Caveat to Eating Fat
The title of this post is a little bit misleading unless we are eating a low-carb diet. There are all sorts of essential fats and fatty acids that you’re body requires to operate efficiently or at all. We get these from our diets and our bodies use them. A widely accepted essential fatty acid are DHA & EPA found in fish oil. Our bodies can not produce these and they must come from endogenous sources such as food. So fat in our diets is a good thing.
Here’s the caveat; if we eat a bunch of carbs the body has to take care of those or try to use them for energy. In that case, then yes, the excess fat in our diets is stored along with the carbs through lipogenesis because we’ve created an energy surplus. Without carbs fueling an insulin response our bodies store much less energy as fat.
Our Bodies Prefer Low-Carb
Writing the previous paragraphs reminded me of another interesting evil of low-fat diets. There is a myriad of essential fatty (EFAs) andamino acids. I won’t go into them in depth here but check the links for the Wikipedia articles. Also, according to Wikipedia (as well as every medical textbook or journal on the subject), “Carbohydrates are a common source of energy in living organisms, however, no carbohydrate is an essential nutrient in humans.”
Limiting fats and proteins in our diets is actually detrimental to our health. Completely cutting out carbohydrates has no ill effects whatsoever.
A few of my friends are worried about my cardiovascular health. After maintaing a low-carb diet for nearly a year of my blood pressure, lipid profile and other markers have vastly improved and are now within the normal range. There are a few journal articles that show a 28% increase efficiency when cardiac muscle is running on ketones from metabolizing fat. Here’s one:
The fundamental reason why the metabolism of ketone bodies produce an increase of 28% in the hydraulic efficiency of heart compared with a heart metabolizing glucose alone is that there is an inherently higher heat of combustion in -β-hydroxybutyrate [a ketone] than in pyruvate, the mitochondrial substrate which is the end product of glycolysis. (Emphasis mine. http://www.ncbi.nlm.nih.gov/pubmed/14769489?dopt=AbstractPlus)
The author of the Johns Hopkins study mentioned in the Times article shared his experience after three years of carb restricted dieting.
Dr. Stewart also has amassed some intimate anecdotal evidence. For a small pilot study several years ago, he became a test subject, adopting a low-carbohydrate diet and regular exercise routine. For three years, he has maintained both the diet and the workouts. He is 40 pounds lighter these days and, he said, continues to ace tests of his blood-vessel health.