The Paleo Diet - Loren Cordain [9]
And although low-carbohydrate diets may be successful in promoting weight loss, many dieters are achieving short-term weight loss at the expense of long-term health and well-being. Here’s what the sellers of these diet plans don’t want you to know: when low-carbohydrate diets cause weight loss in the short term, it’s because they deplete the body’s reserves of muscle and liver glycogen (carbohydrate), and the weight you’re losing rapidly is mostly water weight.
When low-carbohydrate diets cause weight loss in the long run (weeks or months), it’s because more calories are being burned than consumed, plain and simple. Low-carbohydrate diets tend to normalize insulin metabolism in many people, particularly in those who are seriously overweight. This normalization prevents swings in blood sugar that, in turn, may cause some people to eat less and lose weight. It is the cutback in total calories that lowers total cholesterol and low-density lipoprotein (LDL) cholesterol (the bad cholesterol) levels. Also, reductions in dietary carbohydrates (whether calories are cut or not) almost always cause a decline in blood triglycerides and an increase in blood high-density lipoprotein (HDL) cholesterol (the good cholesterol).
So, if low-carbohydrate diets cause someone to consume fewer calories, they may help produce weight loss and improvements in blood chemistry, at least over the short haul. However, dieters beware: when low-carbohydrate, high-fat diets are followed without a decrease in the daily consumption of calories, they are, according to the American Dietetic Association, “a nightmare.” Let’s see why.
Low Carb Doesn’t Mean Low Cholesterol
Despite what anybody tells you—despite the outrageous claims of the low-carbohydrate, high-fat diet doctors—if you eat a lot of the saturated fats found in cheeses, butter, and bacon and don’t cut your overall calorie intake, your cholesterol will go up. The medical community has known this for more than fifty years. It’s been demonstrated in metabolic ward studies, in which people are locked into a hospital wing and only allowed to eat foods that have been carefully weighed and analyzed. Many of the low-carbohydrate diet doctors claim that these clinical trials are invalid because none of them reduced the carbohydrate content sufficiently. These doctors should know better; low carbohydrates don’t guarantee low cholesterol.
Dr. Stephen Phinney and colleagues from the Massachusetts Institute of Technology conducted a normal caloric intake metabolic ward trial involving nine healthy, lean men. These men consumed nothing but meat, fish, eggs, cheese, and cream for thirty-five days. They had a low carbohydrate intake—less than 20 grams a day—but it didn’t matter. Their blood cholesterol levels still went up, from 159 to 208 on average in just thirty-five days. This study indicates that diets high in a specific saturated fat called palmitic acid tends to raise blood cholesterol levels when caloric intake levels are normal.
So, at best, low-carbohydrate, high-fat diets are a temporary fix. At worst, they can cause big trouble in the long run by elevating LDL cholesterol levels, which increases the risk for heart and cardiovascular disease.
Healthy Fats, Not Lethal Fats
One major difference between the Paleo Diet and the low-carbohydrate, high-fat diets we just talked about is the fats. In most modern low-carbohydrate weight-loss diets, no distinction is made between good fats and bad fats. All fats are generally lumped together; the goal is simply to reduce carbohydrates and not worry about fats.
But you should worry about fats. Not all fats are created equal, and the impact of fat on blood cholesterol—and the odds of developing heart disease—can’t be ignored. The problem is, fats are confusing for many people trying to make good dietary decisions. For one thing, many of them sound alike. How are saturated fats different from monounsaturated