Criticism of low-carbohydrate diets is widespread, but are these concerns justified? Here are seven of the most common allegations. Let’s bring them before the court.

I promise what you are about to read may shock you and contradict many of the common beliefs you may have about low-carbohydrate diets. Low-carb diets have been openly ridiculed, condemned and described in every negative light possible by the media and health experts, and nearly every official agency warns of all the dangers of following such a lifestyle.
     But are these scare tactics regarding low-carb eating justified? As a researcher and longtime follower of low-carbohydrate diets, I’ll break it down and get to the truth. Let’s look at the case against low-carb diets one charge at a time.
     Court is now in session.

/// Charge #1 ///
All That Saturated Fat Can’t Be Good
No other nutrient has been demonized more than saturated fat — it directly causes heart disease and diabetes, so the claim goes. But if put to the test in a court of law, the verdict would be “not guilty,” because the evidence against saturated fat is so weak it is almost laughable.
     Consider the recent Harvard study that found the highest saturated-fat intake also had the least plaque buildup on their artery walls. These results were so counterintuitive that a scientific editorial described the findings as an “American Paradox.” But what about the increased cholesterol, you might ask? Yes, plasma LDL cholesterol goes up with increased intake of some types of saturated fat, but replacing carbohydrates with saturated fat — or any type of fat — results in decreased blood triglycerides levels, increased HDL (good) cholesterol levels, and increases in the size of LDL particles, which are a less harmful form of LDL cholesterol.
     And there is more. According to the “you are what you eat” way of thinking, consuming more saturated fat in the diet should lead to increased saturated-fat levels in the body. Here is the kicker: Eating more saturated fat, oddly enough, results in decreased blood levels of saturated fat.
     Preposterous, you say? Not according to results from our laboratory (the Human Performance Laboratory, Department of Kinesiology, University of Connecticut). My colleagues and I recently conducted a tightly controlled diet study where we had overweight men and women adhere to either a low-carb or low-fat diet for 12 weeks. Before and after the experiment, we performed detailed measurements of the participants’ dietary intake and the circulating fats in their blood stream. Those who followed the low-carb diet consumed 36 g of saturated fat per day, over three times more than those eating the low-fat diet. Yet despite this greater intake of saturated fat, the low-carb dieters dramatically reduced their blood levels of saturated fatty acids by an astounding 57%, compared to 24% in the low-fat group.
     Where did the saturated fat go? Easy. When carbs are low, the body manufactures less and burns more saturated fat. The idea that came out of this study was that carbs control the fate of fat. When carbs are low, saturated fat is handled more efficiently. More accurately, “you are what you do with what you eat.”

Ruling From The Court: Excess carbohydrate, not saturated fat, is the villain. This is the paradigm shift emerging from the latest work in nutrition science.

/// Charge #2 ///
Low-Carb Diets Are Deficient In Nutrients
No food group contains all the essential nutrients our bodies need, so dietary recommendations encourage people to eat a variety of foods. Since a low-carb diet requires you to limit certain foods such as breads, pasta, potatoes and rice, critics like to point out that the diet is lacking in several important nutrients. However, reducing fat eliminates even more foods and nutrients than restricting carbohydrates. My colleagues and I have studied vitamin and mineral intakes in free-living individuals on both low-fat and low-carb diets. The results showed that several vitamins (vitamin E, riboflavin, niacin, B-12, biotin and pantothenic acid) and minerals (calcium, phosphorus, magnesium, zinc and selenium) were significantly higher on a very-low-carb diet.
     But how can a diet that lets you eat all the bacon you want be nutrient-rich? Maybe no one actually eats pounds of bacon on a low-carb diet. In fact, researchers who studied an Internet support group, called the Active Low-Carber Forums (www.forum.lowcarber.org), found just that. This is a group with more than 86,000 members who follow a low-carb diet. The study documented behaviors and attitudes of these people on low-carb diets. There was a high level of satisfaction, indeed enthusiasm, for low-carb dieting. Most notably, the survey identified 1,088 people in a one-month period who lost greater than 30 lb and maintained the weight loss for more than a year. The major dietary change was not an increase in bacon, but rather a large increase in green vegetables and replacement of starch and sugar-containing foods with nonstarchy vegetables.

Ruling From The Court: Low-carb dieters get plenty of nutrients and appetite satisfaction from their food.

/// Charge #3 ///
Ketones Are Toxic
“Ketones are toxic.” I wish I had a dime for every time I heard that one. I guess the highly respected researchers who published the following article didn’t get that memo (Cahill GF Jr, Veech RL. Ketoacids? Good medicine? Trans Am Clin Climatol Assoc. 2003;114:149-61).
     Ketones are a by-product or a waste product when your body burns stored fat for energy. The scientists from the study above actually refer to ketones as “superfuel” and describe therapeutic uses of ketones for a variety of disease states. Why do ketones get such a bad rap?
     First, there is confusion between the ketosis that develops with carbohydrate restriction with diabetic keto-acidosis, a life-threatening state that can occur in type 1 diabetics who aren’t treating their condition appropriately. Nutritional ketosis, on the other hand, is simply a term used to describe the normal process of producing and using ketones for energy. When ketones are produced, it indicates fat is being broken down rapidly. Ketones are used for energy and spare breakdown of muscle protein. Ketones also suppress your appetite.

Ruling From The Court: Far from being toxic, ketones could just be the perfect fuel for dieters.

/// Charge #4 ///
Eating Fat Makes You Fat
Should we fear fat? After all, gram for gram, fat has more than twice the calories compared to carbs. Thus, reducing fat in the diet would appear to be the most efficient way to reduce calories.
     Nice theory, except it is wrong. Government statistics on food consumption show that fat intake has not changed much, while carbohydrate intake has gone up precipitously over the same time obesity rates have skyrocketed. What happened was people replaced fat with an even greater amount of carbohydrate. So much for the “eat fat, get fat” theory.

Ruling From The Court: Increases in carb consumption, not dietary-fat consumption, have risen dramatically with overall obesity rates.

/// Charge #5 ///
A Calorie Is A Calorie
The “calorie is a calorie” theory of weight management boasts that the types of foods you eat don’t matter, only the total amount of calories. Low-carb-diet critics love to cite the first law of thermodynamics as evidence that you can’t lose more weight on a low-carb diet. If you’re rusty on physics, the first law goes like this: The amount of energy your body stores equals the amount of energy you consume minus the amount of energy you expend. Simply put, if you eat more calories than you burn, you’ll store the entire excess.
     The question posed is whether it is possible to lose more weight on a low-carb diet without restricting more calories. Study after study has shown it is possible. In fact, a 2003 study at Harvard University found that low-carb dieters lost more weight in 12 weeks than low-fat dieters despite eating 300 more calories a day. In our own studies, we have seen over and over again greater weight loss with low-carb diets than low-fat diets, despite similar caloric intake. Others have shown similar effects.
     Are these studies an example of a blatant violation of that first law? If not, how do you account for the loss in calories? Several possible mechanisms have been put forth, including the thermic effect of protein, stimulation of uncoupling proteins that increase heat loss, loss of energy in ketones and increased energy loss through metabolic processes required to make glucose.

Ruling From The Court: In most comparison studies, weight loss was almost exactly two times greater with the subjects consuming a low-carb diet. In fairness, not all studies have shown greater weight loss (the reasons are unknown why), but certainly the majority do.

/// Charge #6 ///
Health Benefits Of Low-Carb Diets Are Due Solely To Weight Loss
Since low-carb diets often result in greater weight loss than low-fat diets, any improvements in other metabolic markers of disease risk that improve on low-carb diets are attributed to the weight loss, not the carbohydrate restriction. Again, here the evidence actually suggests exactly the opposite. Low-carb diets consistently result in better responses in all the features associated with metabolic syndrome, a condition associated with increased risk of diabetes and heart disease. This includes improved triglycerides, increased HDL cholesterol, decreased glucose, decreased insulin and reduced body fat.

Ruling From The Court: Recent studies show that these metabolic benefits of low-carb diets are independent of weight loss, whereas low-fat diets often worsen these markers unless weight loss also occurs.

/// Charge #7 ///
Your Body Needs Glucose To Survive
A major misconception about very-low-carb diets is that you don’t have glucose available for energy. Low-carb diets are claimed to deprive the brain of glucose and reduce mental capacity.
     However, your brain only requires a very small amount of glucose, especially after a few weeks when adaptation to using ketones as an alternative fuel takes place. Also, it turns out the body is perfectly capable of making glucose from other noncarbohydrate sources. The process is called gluconeogenesis (gluco = glucose; genesis = formation). Thus, the body is quite adept at making all the glucose it needs without consuming any carbohydrate.

Ruling From The Court: Low-carb diets result in very stable glucose levels throughout the day compared to the fluctuations that occur on a low-fat, high-carb diet.

/// Final Judgement ///
Low-carb diets are an easy target. The idea of replacing carbohydrates with fat and protein is contrary to every dietary guideline put forth by government-sponsored health organizations for the last 30 years.
     For three decades, we’ve been fed the virtues of a low-fat lifestyle. And in that time, the number of overweight Americans has inflated to more than 60%, with major diseases rising to an all-time high. Our government also spent more than $500 million on a trial designed to show once and for all that low-fat diets reduce risk for disease. The study results were published earlier this year and showed absolutely no effect.
     We don’t have all the answers yet, but I’ve outlined seven of the most frequently mentioned myths and brought the case against them. Shouldn’t we be critically evaluating the current evidence and work to help people choose the best diet that works for them? The first step is becoming educated. Consider this article part of that journey to knowledge.
     Case closed.