THE LOW-CARBOHYDRATE ALTERNATIVE
The fact that the nation is awash in an epidemic of obesity and related chronic diseases after so much “progress” has been made in the area of nutritional science must rank as one of the great ironiesof our time. The debate over what constitutes an ideal diet appears to be never-ending. No sooner does an apparently authoritative source recommend one thing, with a study to back it up, than another equally authoritative source suggests something completely different, backed up with other research. Much confusion ensues and in their growing disenchantment with authoritative sources, people tend to become unresponsive to any nutritional advice whatsoever. Who can blame them?
Questions About Carbohydrates
Here are some areas in which the science is clear. We get our energy mainly from three macronutrients: fat, protein and carbohydrate. There’s a limit in terms of how much protein we can eat. If we eat too much we’ll feel ill. Consequently, the majority of our calories must come from fat and carbohydrates. The major questions, therefore, revolve around fat vs. carbohydrates. Specifically,how much of each is ideal? And which fats and which carbohydrate foods are healthy and which should be avoided? Interestingly, of the three macronutrients, only protein and fat are essential to our survival. We can do fine eating very few carbohydrates in the form of vegetables since the liver is quite capable of producing all the glucose needed for the few tissues that are truly glucose dependent.
The Standard American Diet
Perhaps the one thing that’s clear from this debate is that there are no clear answers. It’s quite possible that different dietary advice may be appropriate for different people. There may be no “one-size-fits-all” diet. The one area of general agreement is that what we call the standard American diet (SAD) is definitely not ideal. This diet is high in calories, fats, sugars and refined carbohydrates. Most of the prescribed diets eschew one or more of these elements. And when a person adheres to a prescribed diet, whether it’s low fat, low calorie, low carbohydrate, vegan or otherwise, it will inevitably demonstrate an improvement over the SAD. This allows the proponents of a given diet to proclaim its virtues but doesn’t help us understand which, if any, of the prescribed diets may be best overall. Or which is best suited to a particular individual’s needs.
The Role of Insulin Resistance
From this somewhat chaotic situation, some emerging research has helped us understand the specific dietary needs of a large subset of the population. It's becoming increasingly clear that people who suffer from conditions associated with insulin resistance benefit from a carbohydrate-restricted diet. Insulin resistance is the metabolic defect underlying type 2 diabetes. However, it can be present for many years before symptoms appear or routine blood tests detect it. It’s implicated in obesity and ties together a constellation of problems we call “metabolic syndrome” or “pre-diabetes.” These include abdominal weight gain, high blood pressure and cholesterol problems, all of which are common conditions today.
A number of research trials have shown consistently that the problems associated with insulin resistance improve, sometimes dramatically, when carbohydrates are restricted. This makes intuitive sense if you consider that, by definition, insulin resistance means you are no longer able to normally metabolize carbohydrate foods. In other words, you’ve acquired a de facto carbohydrate intolerance. The recent research is telling us that, as with other food intolerances, if you avoid the offending foods, the associated problems get better. While this may seem like a radical idea, a quick look at the history of diabetes tells you it’s not. This was the standard therapy for diabetes in the days before the discovery of insulin.
The Fat Issue
So, why does this simple and effective therapy meet with so much resistance? In a word: fat. If you restrict carbohydrates, you’ll need to get the bulk of your energy from dietary fat and we have been told that fat is bad, especially saturated fat. How often have you seen it referred to as “artery-clogging fat”, evoking that graphic image of hot bacon grease choking the cold kitchen drain? It turns out that neither does the clogging of arteries work that way, nor does saturated fat in your diet play a significant role. Overall, the studies that look at fat consumption fail to correlate fat consumption with obesity rates. And studies looking specifically at saturated fat also fail to correlate it with arterial disease.
So how is it that we have a nutritional science consensus telling us to avoid fat in our diet? You’d have to read Gary Taubes’ excellent book, "Good Calories, Bad Calories," to truly understand how this error has come about. Suffice it to say that the evidence was never particularly strong and has recently been well and truly debunked. And, it takes a long time to turn an aircraft carrier around.
Poorly Designed Studies
Further confusing the picture is the fact that studies purporting to test a low-carbohydrate high-fat diet are often poorly done. In addition, the standard way of analyzing study results tends to obscure the beneficial effects of a diet if the overall compliance is low. There are many ways to do a low-carbohydrate diet poorly which will certainly reduce success and increase drop-out rates. Unfortunately, too many of the reported studies suffer from these problems. To truly understand the potential benefits of a low-carb diet one must look at well executed studies with high compliance rates.
Well Designed Studies
Researchers at the University of Connecticut, led by Dr. Jeff Volek, have been doing such studies.Their findings are nothing short of remarkable. People with insulin resistance who eat a very low-carbohydrate diet rich in fat improve enormously. Not only does their weight drop and their insulin resistance correct, but they also improve arterial function and achieve enviable cholesterol readings. When their blood is tested for saturated fat, the levels are actually lower than those of control subjects who are eating far less saturated fat. It appears that removing most carbohydrates from the diet allows for the more efficient burning of saturated fat. The correction of insulin resistance also allows for stored body fat to be released and burned which makes the pounds fall away in a seemingly effortless fashion.
Other studies have demonstrated that restriction of carbohydrates also reduces appetite, which explains why low-carb dieters typically report reduced hunger even as they lose weight. This perhaps also explains why, in a number of trials, compliance with a low-carb diet is higher than that of a calorie-restricted diet. It's hard to stick to a diet if you are hungry all the time.
A Sustainable Approach
While it appears that a very low-carb diet is ideal for people with insulin resistance, does that mean it is ideal for everyone? The evidence to support that contention is less conclusive. On the other hand, there’s no evidence that carbohydrate restriction causes harm. That much cannot be said for the SAD. Whether you choose low-carb, low-fat, vegan, paleo or any other prescribed diet, the benefits you achieve will depend on two factors: are you meeting your requirement for essential nutrients and can you stay on the diet for the long-term? While long-term compliance is an issue with any diet, success in sustaining a low-carb diet will depend on getting comfortable with eating fat. Hopefully, the recent evidence vindicating fat, and specifically saturated fat, especially in the context of a low-carb diet, will encourage more people to maintain carbohydrate restriction and to benefit from the improvements this w ay of eating brings to their cardiometabolic risk profile.