The Downsides of Low-Carb Diets
What raises blood sugar? The simple answer is carbohydrates. So why not just yank them out of your diet like weeds in your garden? Why not quash blood sugar by swearing off bread, pasta, rice, and cereal? Been there, done that. The low-carb craze is on the downswing, and that’s a good thing because over the long haul, very low carb diets simply aren’t good for you. That doesn’t mean it’s not smart to cut back on carbs—but don’t go crazy.
When low-carb diets first became popular, they seemed to be a breath of fresh air after the low-fat (and high-carb) diets that preceded them. Remember low-fat cookies, lowfat snack cakes, and low-fat everything else? With low-carb diets, suddenly people could load up on bacon and still lose weight as long as they were willing to eat hamburgers without buns and pretty much give up sandwiches and spaghetti. People were amazed at how effective these diets could be. Weight loss could happen very quickly, sometimes within days. And amazingly, it often seemed to come with added health benefits, including lower cholesterol, blood pressure, and triglycerides (blood fats linked to heart attacks.)
The most extreme kind of low-carb diet was pioneered by the late Robert Atkins, M.D., whose first book, Dr. Atkins’ Diet Revolution, came out in 1972. It promised quick and long-lasting weight loss and prevention of chronic disease, all while allowing high-fat steak and ice cream. Since then, other, more moderate low-carb diets have allowed small amounts of carbohydrate-rich foods, but they still cut out most grains as well as starchy vegetables and even fruit.
The Atkins diet and the many other low-carb diets that followed in its footsteps have turned out to be less effective, and less healthy, than originally claimed. Often, the weight returned, and as it did, problems such as high cholesterol and high blood pressure came back, too. Also, in the end, many people decided they didn’t want to go through life without ever eating pasta again. Let’s look at what would happen if you followed one of the more extreme low-carb diets.
You’ll Feel Terrible
Low-carb diets usually begin with an “induction” phase that eliminates nearly every source of carbohydrate. Often, you’ll consume as few as 20 grams of carbohydrate a day. That’s less than 100 calories’ worth—about what’s in a small dinner roll. On a 1,200-calorie diet, that’s only about eight per cent of your daily calories. By contrast, health experts recommend that we get between 45 and 65 per cent of our calories from carbs.
When carbohydrate consumption falls below 100 grams, the body usually responds by burning muscle tissue for the glycogen (stored glucose) it contains. When those glycogen stores start to run out, the body resorts to burning body fat. But that’s a very inefficient, complicated way to produce blood sugar. The body tries to do it only when it absolutely has to (such as when it’s starving)—and for good reason. Turning fat into blood sugar comes at a price in the form of by-products called ketones. They make your breath smell funny. They can also make you tired, lightheaded, headachy, and nauseated. Feeling lousy is certainly one way to dampen the appetite, but not one that most people would choose.
With virtually no carbs in your system, you may even have trouble concentrating. According to the Institute of Medicine of the National Academy of Sciences, the human brain requires the equivalent of 130 grams of carbohydrate a day to function optimally—and that’s a minimum.
Your Health May Suffer
If you’re overweight or obese, and you have insulin resistance—and especially if you have prediabetes or diabetes—cutting way back on carbohydrates can have immediate health benefits. Your blood sugar and insulin levels will go down, your triglycerides and blood pressure may fall, and your levels of “good” HDL cholesterol may rise.
But the low-carb diet will also wreak some havoc. When your body breaks down lean body mass—muscle—for energy, your metabolism slows because muscle tissue burns up a lot of calories. This may be one reason that the weight often comes back after you’ve been shunning carbs for a while.
The effects on your heart are also questionable. Especially if you switch to a high-saturated-fat diet, as people do when they start eating their fill of steak and bacon, your “bad” LDL cholesterol will go up. Levels of homocysteine, an amino acid that increases the risk of heart disease, may also rise if you eat a lot of meat and too few vegetables. And to get rid of the ketones produced when your body burns fat for energy, your kidneys need to work overtime, which raises your risk of kidney stones.
Ironically, low-carb diets may even interfere with insulin sensitivity; a certain amount of carbohydrate in your diet may be needed in order for the pancreas, which produces the insulin that keeps blood sugar in check, to work well.
You’ll Miss Out
It’s not just that you’ll feel deprived because you’ve had to give up bread, fruit, and all the rest. Your body will also be deprived of foods and nutrients that are essential for good health, including the following.
- Whole grains: These protect against metabolic syndrome, diabetes, heart disease, stroke, and cancer.
- Fruits and vegetables: Produce helps prevent heart disease, stroke, and some cancers. Most fruits and vegetables are very filling while providing few calories, so they can help you cut calories without deprivation. Indeed, the more fruits and vegetables people eat, studies show, the thinner they tend to be.
- Beans: Rich in protein, complex carbohydrates, and B vitamins, beans have no saturated fat and lots of soluble fibre. They also contain plant chemicals that protect against heart disease and cancer.
- Low-fat dairy foods: Sure, you can have butter and cream on a carb-restricted diet, but you won’t get much calcium or protein from them. Fat-free and low-fat versions of milk and yogurt are excellent sources of those nutrients.
- Fibre: Getting fibre from these foods (except dairy) helps reduce the risk of heart disease and diabetes. Beans and many fruits and vegetables are particularly rich in soluble fibre, which helps lower blood sugar, curbs hunger, and lowers LDL cholesterol.
- Vitamins, minerals, and health-protective plant chemicals: Whole grains, for example, are rich in components such as lignans, which may protect against diabetes independently of their effects on blood sugar. And without fruits and vegetables, you’d be awfully hard-pressed to get enough vitamin C or other disease-fighting antioxidants.
You’ll Eat Too Much “Bad” Fat
The original Atkins diet became popular largely because it allowed people to eat foods forbidden on most other diets, such as cheeseburgers (without buns). More recently, the diet has been revised to include sources of healthier fats, such as fish and olive oil, and other low-carb diets have shied away from saturated fats as well. But in practice, once you stop eating bread, fruit, and beans, it’s all too easy to eat too many fatty animal foods. After all, how many foods can you take out of your diet?
If you load up on saturated fats—the original Atkins diet got as much as 26 per cent of its calories from saturated fat versus the 10 per cent or less that experts recommend—it’s bad for your health. Saturated fats are still the major culprits behind elevated LDL cholesterol. The latest revisions to the diet, to be fair, do emphasize lean poultry and seafood, but in practice, many people are attracted to this diet for the bacon and butter.
What’s more, saturated fats also directly impair the body’s ability to react to insulin, so following a low-carb, high-saturated-fat diet may help you lose weight in the short term, but it may also speed the development of insulin resistance. Eventually, that can lead to metabolic syndrome, diabetes, and heart disease.
The Weight Will Come Back
Two major studies of low-carb diets, published in the New England Journal of Medicine, looked at obese men and women who stuck with either a low-carb, high-fat diet or a low-fat, high-carb diet. Both diets were low in calories.
In one study, which lasted six months, the low-carb diet seemed to win hands down. The people on it lost nearly 13 pounds (6 kg); the low-fat dieters shed just 4 pounds (2 kg). But the second study lasted six months longer, revealing a truth about low-carb diets: The results don’t last. This study too found that the low-carb dieters lost more weight in the first six months, but in the second half of the year, the weight came roaring back. By the end of a year, there was no significant difference in weight loss between the two groups. This weight “snapback” may be one reason that extremely low-carb diets have fallen out of favour.
Take the Good, Leave the Bad
The good news? Many of the weight-loss advantages of low-carb diets may have nothing at all to do with restricting carbohydrates. The main benefit may be due to the extra protein—and you can add protein to your diet even if you don’t drastically cut carbs. Protein-rich foods can really help with weight control. One reason may be that protein stimulates the body to burn slightly more calories than carbohydrates or fats do.
The main reason, though, is that protein foods curb hunger better. When people eat protein-rich foods, they feel fuller longer, and when they diet, they consume fewer calories and lose more weight when they eat a lot of protein.
One recent study puts it in perspective. Researchers at the University of Washington School of Medicine in Seattle gave volunteers a diet that got 50 per cent of its calories from carbohydrates. That’s certainly not a low-carb diet, though it’s not a high-carb diet either. It’s actually a good goal, on par with what we suggest.
To start, the volunteers got only 15 per cent of their calories from protein and 35 per cent from fat. That’s about what most people get. Then they switched: Carbs stayed the same, but fat was decreased to 20 per cent of calories, and protein was doubled to 30 per cent. The participants were allowed to eat as much as they wanted— but they ate less. Over 14 weeks, they lost an average of 11 pounds (5 kg), including 8 pounds (3.5 kg) of body fat, thanks to the extra protein.
More Protein, and Carbohydrates in Moderation
No matter how you slice it, we eat too many carbohydrates. We consume many more calories than we used to, and most of those extra calories come from extra carbs (so many chips and cookies!). Thus, it makes sense to cut back some on carbs. It also makes sense to choose lower-GL carbohydrate foods instead of “fast-acting” carbs that send your blood sugar soaring. These strategies are a big part of the Magic Foods approach to eating.
That approach provides the benefits of a drastically low-carb diet with none of the hazards. You’ll get the blood sugar advantages, including lower insulin levels. By eating plenty of lean protein, you’ll feel satisfied and less hungry. And by choosing “good” fats and limiting “bad” ones, you’ll keep LDL cholesterol from rising and protect your heart in the process. You’ll also discover a way of eating that you can enjoy—rather than endure—for the rest of your life.