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Carbohydrates and Body Fat ?awB%vgyOV
Big Fat Lies About Carbohydrates and Body Fat
In fitness circles, few subjects generate more intense debate these days than weight loss. One of the primary issues being debated is what amount of carbohydrate, protein and fat is best for achieving weight loss and maintaining weight loss. In other words what is the optimal composition of a diet that is designed to assist in weight management.
In recent years several books have been recycled (from the 70’s), and new books have surfaced, suggesting that the best way to manage body weight is to limit all foods that raise insulin levels. It has been suggested by some self-proclaimed diet guru’s that high insulin levels promote obesity and all the metabolic problems associated with it.
The leader of the pack is clearly Dr. Robert Atkins a New York City cardiologist who in the 1970’s published the first edition of his best selling book “Dr. Atkins Diet Revolution”. Others have followed since then taking various approaches to explaining why insulin is the culprit, and that any food which raises insulin should be limited, and in some cases completely avoided.
So why has insulin (a hormone our bodies need to function normally) gotten such a bad rap? Biologically speaking insulin is what we call an anabolic (tissue building) hormone. Its job is to get fuel (in most cases blood sugar) into cells where it can be used as an energy source. Insulin also plays a key role in the formation of fat (adipose tissue) and muscle. Without insulin our bodies would self-destruct and break down stored carbohydrate, fat and muscle for fuel. This is exactly what happens to a diabetic when they experience uncontrolled diabetes. They experience body wasting (lose body fat and muscle).
If insulin is the bad guy, it would make perfect sense to track insulin levels throughout the day in an effort to keep it low. In theory this could help prevent the accumulation of unwanted body fat. While this sounds good on paper, it cannot be done practically speaking. However insulin levels go up when blood sugar goes up. Therefore it would be easier to simply rate foods based on how much they raise blood sugar. The degree to which a given amount of food eaten by itself on an empty stomach raises blood sugar is what we call “glycemic index”.
Historically it was believed that simple carbohydrates (sugars) produced a significant rise in blood sugar and insulin, while complex carbohydrates produced a more gradual rise in blood sugar and insulin. However in the early 80’s, nutrition researcher David Jenkins at the University of Toronto published data that ranked carbohydrate rich foods, based on how much of an effect these foods had on blood sugar and insulin levels. Dr. Jenkin’s data turned conventional wisdom upside down suggesting that not all complex carbohydrates break down slowly producing a gradual rise in blood sugar. Since the 80’s additional work has been done measuring glycemic index of various foods.
While there is nothing wrong with determining the glycemic index of a food, it does not make sense to base your entire diet on this concept. At first glance it seems pretty simple to suggest that everyone avoid foods with a high glycemic index because those foods raise blood sugar. When blood sugar levels rise, that “fat forming” hormone insulin also goes up.
Once again, this concept sounds great on paper, however it does not take into account several critical factors. First, and probably most important is the fact that carbohydrate rich foods contain varying amounts of carbohydrates. The carbohydrate density (how many grams of carbohydrate the food contains per ounce) of carbohydrate rich foods varies widely. An example would be dry cereal at 110 calories per ounce versus carrots at 10 calories per ounce. Both of these foods have a glycemic index over 100, yet when eaten in a real world diet provide different amounts of calories. It would be very easy to consume two cups of cereal at breakfast providing approximately 250 calories while you would have to eat approximately 5 cups of raw carrots to get that many calories.
Therefore two foods with the same glycemic index can produce significantly different increases in blood sugar and insulin levels. As a result, it does not make sense to base decisions about food choices exclusively on glycemic index.
A better way to evaluate carbohydrate rich foods in the context of good nutrition, weight management, and health is to look at the “glycemic load” of that food. According to Dr. Walter C. Willett, MD of Harvard University “although the glycemic index of a food is helpful information, it is only part of the story, because the effect of eating a food on blood glucose and insulin levels depends on both the amount of carbohydrate and the glycemic index of that carbohydrate”(1).
While it would be easy to focus 100% of your energy on glycemic load, given that it seems to look at the whole picture, Dr. Willet also warns against that approach. He states that “while the glycemic load is a useful tool for deciding what to eat, don’t build your whole diet around it. Some carbohydrate-rich foods deliver far more than just blood sugar. Fruits and vegetables offer fiber, vitamins, minerals, and plenty of phytochemicals”(1).
The take home message from Dr. Willet is very clear. Both the amount and type of carbohydrate are what matters. Therefore, it would be overly simplistic to say that obesity in America has gone up because we are eating too much carbohydrate.
In reality, American’s are eating more processed carbohydrates which translates into more empty calories. At this point in time there is absolutely no published data anywhere in the world indicating a diet rich in high quality carbohydrates (such as whole fruits, vegetables and whole grains) leads to increases in body fat. In fact, there is overwhelming data supporting just the opposite! One compelling study that supports this thinking was published in the American Journal of Public Health in 1997. In this study the American Cancer Society tracked 79,000 men and women for 10 years looking for behaviors that prevented weight gain. The authors of this study concluded that a high intake of vegetables (3 or more per day) was protective against weight gain in the abdomen. There are obvious reasons why eating more vegetables would lead to a lower body weight. Not only are vegetables very low in calories, they also displace higher calorie foods at meal time.
Even the much maligned baked potato is a good choice given what is usually served up for dinner in America. A baked potato topped with another vegetable and served with a lean protein is an excellent lunch or dinner choice. At only 20 calories per ounce baked potatoes are significantly lower in calories than the more common form of potatoes, French Fries, at 100 calories per ounce. Take it a step further and you get potato chips (even higher in fat) at 150 calories per ounce. I know it’s not exciting and doesn’t sell diet books but in reality calories do count. When you over eat and consume more calories than you require you gain weight.
It really is quite unfortunate that consumers have to be exposed to information such as the misleading statements made by Dr. Atkins. In his latest book he states that American’s are not overeating. He blames obesity on a metabolic problem that can only be solved by following his diet. Isn’t it interesting that independent analysis shows people who follow the Atkins diet consume substantially fewer calories when “on-the-diet”. Duke University recently reported that a group of people they tracked on the Atkins diet ate fewer than 1500 calories per day. At least Dr. Atkins could be honest about it and tell his readers that they will lose weight on his diet due to the fact that they are eating fewer calories. In fact every diet ever developed since the 1800’s has been a different version of the same thing (a low calorie food plan). The only thing that changes is the emphasis. One may emphasize carbohydrates, while another may focus on fat, and so on.
In my opinion even the most untrained consumer of health information realizes that American’s are eating too much. A study that looked at this very issue was published earlier this year in the American Journal of Public Health. This study looked specifically at restaurant food. The investigators in this study reported an average increase in portion size of between 200 to 700% over the past 30 years.
They also went on to say that portions are continuing to increase. Let’s be perfectly honest about this. When was the last time you ate a meal in a restaurant, looked around you, and noticed that everyone in the place was eating an amount of food that was “just right” for their body.
I think this problem can be best summarized by the words of Kelly Brownell Ph.D, professor of psychology at Yale University. Dr. Brownell states that Americans are exposed to a “toxic” food environment. I would agree with Dr. Brownell and add that the sooner Americans realize that they need to eat fewer calories, the better off they will be. Obesity is an environmental problem that is getting worse because the environment is getting worse. Portions are out of control while the use of energy conserving devices continues to rise. The US Dept. of Health and Human Services just reported that the percentage of American’s who report engaging in no physical activity just went up from 25% to 40%. This is a painful reminder that we need to continue to reach more people.
So what is the bottom line for weight loss? Only by reducing calorie intake can a person lose weight and keep it off. Over the past 15 years I have achieved great success with my clients by recommending a diet that emphasizes decreasing calories by decreasing intake of both refined carbohydrates and saturated fat. Adequate high quality protein is always essential as well as consistent physical activity.
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