The Inconvenient Truth About Carbs
November 5, 2007
By Donna Shaw B.Sc. MBA
The skinny on what’s good for us …
Concern for carbs taking slices out of your business? Consider that one out of every two of your customers is either obese or overweight, and, as a result, up to 40 per cent of women and 25 per cent of men are dieting at any given time1. Therefore, it is likely that at some point, your customers will ask you about foods that are available for healthy weight loss.
Despite the controversy surrounding low-carbohydrate diets (i.e., the recommendation of the elimination of virtually all bread and other baked goods from the diet), many Canadians still believe that this diet plan will offer them an easy and effective weight loss solution. Here’s what you need to know to offer scientifically sound, nutritional information to your customers about the importance of carbohydrates, especially those that are low on the glycemic index, and their impact on weight loss.
The (inconvenient) truth
Anyone trying to lose weight is likely to be familiar with low-carbohydrate diets – the most famous of which is the one proposed by Dr. Atkins, most recently released as Dr. Atkins’ New Diet Revolution1. The level of attention this low-carbohydrate diet regime received over the past several years has been phenomenal — with most of the attention focused on its “anything goes” attitude towards saturated fat and protein. The inconvenient truth is that the science behind low-carbohydrate diets is misleading, the long-term results are disappointing, and the health risks are often overlooked. The truth about low-carbohydrate diets needs to be brought to light.
How low can you go?
Dr. Atkins’ low-carbohydrate diet claims spectacular weight loss results, despite liberal consumption of fatty meat, butter and other high-fat dairy products. While this description of a diet may sound like a dream, there is a catch. Dieters on Atkins have to eliminate virtually all carbohydrates from their diet (i.e., carbs from whole grains, vegetables and fruits) in order to “trick” the body into believing that it is starving. Consider that the Recommended Dietary Allowance (RDA) for carbohydrates, just for brain function alone, is 130 grams per day for adults2. Compare this figure with the restricted amount of 20 to 30 grams of carbohydrate per day on the Atkins diet plan1, and you can see how low you have to go.
Just the facts
Here are the basics of what you need to know about carbohydrate metabolism. First, carbohydrates from our food (i.e., whole grain breads, vegetables) are digested (i.e., metabolized), primarily into glucose. Second, as glucose from our food enters our blood, insulin is released. Third, insulin transports glucose to the body’s cells for energy, and it also converts excess glucose (i.e., what you eat in excess of what you need) to fat.
Our nutrition goal is to keep glucose and insulin levels in the normal range. If glucose levels are too high, there is an over-supply of insulin, which causes a rapid uptake of glucose by the cells, and, consequently, a low blood glucose level. This “sugar low” leaves us feeling hungry, which tends to cause us to overeat, leading to excess weight gain, and an increase in our risk for Type 2 diabetes. When it comes to selecting carbohydrates in our diet, the rule for both glucose and insulin is “slow and steady.”
The ‘fat-burning’ machine
The author of this relatively old theory of weight loss (low-carbohydrate diets were made popular in 1860 by William Banting), claims that diets high in carbohydrates cause obesity. The approach promoted (for commercial, not scientific, gain) by Dr. Atkins, is loosely based on the evidence described above, that insulin promotes the storage of fat1.
Dr. Atkins postulates that when carbohydrate intake is low, insulin level is also low. As a result, fat storage is not only minimized, but the body is forced to use the existing stored body fat as an alternate source of energy. According to Dr. Atkins, a low-carbohydrate diet turns our bodies into “fat-burning” machines.
Oops – did the truth slip by?
Before you give up your whole grains and vegetables, consider a few things Dr. Atkins forgot to tell you.
First, proteins also stimulate insulin secretion3 – therefore, the conversion of excess glucose to fat continues even without carbohydrates in the diet.
Second, the process of breaking down fats in the absence of glucose to produce energy is call ketosis, and the result is ketones. Ketones may suppress the appetite, but they also cause dehydration and bad breath. If a low-carbohydrate diet is continued for an extended period, the body will produce high ketone levels, causing the blood to become acidic, and resulting in a state of ketoacidosis. Ketoacidosis causes the loss of lean muscle mass and damages body tissues. People with untreated diabetes are at high risk of ketoacidosis, which can lead to coma, and even death2.
And third, low-carbohydrate diets are associated with:
• low energy levels, due to reduced carbohydrate energy for brain functions
• constipation, because of inadequate fibre in the diet
• bad breath, as a result of changes in metabolism
• a depletion of the micronutrients commonly found in complex carbohydrates (i.e., vitamins and minerals, especially vitamin B1, vitamin B6, folic acid and antioxidants)
• a reduction in muscle glycogen stores – a problem for people who want to be active (an important component of an effective weight loss program)
• an increase in blood cholesterol levels, as a consequence of the increased consumption of fat and protein3,4.
What about weight loss?
Even if you can stomach the side-effects associated with low-carbohydrate diets, the scientific evidence continues to demonstrate that these diets are not effective for long-term health and weight maintenance3,4. In fact, a number of clinical trials comparing low- versus high-carbohydrate diets have shown no long-term (i.e., after one year) difference in weight loss3,5.
Why then, do so many people staunchly support the Atkins diet? According to the literature, the short-term difference in weight loss, between high- and low-carbohydrate diets (1 to 2 kg), is often attributed to3:
• rapid loss of body water as opposed to loss of body fat
• calorie, not carbohydrate, restriction. In other words, dieters who lose weight on low-carbohydrate diets have simply reduced their overall caloric intake.
• improved compliance due to high expectations of weight loss caused by the media hype.
What seems to be working on Atkins is compliance to a reduced caloric diet. And that’s nothing new.
Who needs carbohydrates?
We all do! Carbohydrates are an excellent source of energy for all our cells. Fats and even proteins can also be used for energy; however, our red blood cells, brain cells and other nervous tissue rely primarily on carbohydrates. This explains why people feel tired, irritable and even shaky when they miss a meal or go for a prolonged period of time without eating2.
According to Health Canada, carbohydrates should account for approximately 55 per cent of our total daily calories6. The range of carbohydrate consumption associated with a decreased risk of chronic disease is 45 per cent (older and less active adults) to 65 per cent (active adults)2.
For example, if a person normally consumes 2,000 total calories per day, carbohydrates should represent roughly 1,100 calories or 300 grams (four calories of energy per gram). In terms of daily servings, the guidelines suggest six to eight servings of grain products and seven to 10 servings of vegetables and fruit each to day to ensure adequate intake of carbohydrates. A typical serving of carbohydrates is one piece of bread or half a cup of pasta.
All are not equal
You have probably heard there are two kinds of carbohydrates: simple and complex. Simple carbohydrates are sugars from healthy choices such as fruit and milk, but simple sugars are also found in unhealthy choices such as soft drinks, fruit punches and candy.
Simple carbohydrates in foods with added sugar can cause rapid fluctuations of both blood glucose and insulin levels, leading to the “sugar low” discussed previously; whereas, complex carbohydrates cause a smooth rise of both – as a result, you feel full longer.
Over consumption of unhealthy simple sugars can lead to increased levels of triglycerides and LDL (the “bad” cholesterol), as well as decreased levels of HDL (the “good” cholesterol) – all known risk factors for heart disease.
Most health experts agree that the majority of the carbohydrates should be complex – i.e., whole grains in bread and pastas, as well as brown rice, beans, lentils and vegetables.
Complex carbohydrates contain fibre that can2:
• reduce the risk of colon cancer
• prevent hemorrhoids and constipation
• reduce heart disease by reducing blood cholesterol levels
• reduce obesity by making people feel fuller
• lower the risk of Type 2 diabetes by slowing the release of glucose into the blood.
The glycemic index (GI)
The glycemic index refers to the potential of foods to raise blood glucose levels.
Why do we care about the GI? Because high GI foods can cause a rapid increase in both glucose and insulin, and as discussed previously, this can lead to health problems such as weight gain and an increased risk of Type 2 diabetes.
Foods with a high GI (i.e., cold cereal) are digested quickly, causing a spike in both blood glucose and insulin levels. As mentioned, insulin works to move the glucose from the blood into body cells for energy — which is good; but, remember, too much insulin can cause glucose levels to plummet, leaving us feeling hungry and likely to overeat, which is not so good.
Conversely, foods with a low GI (i.e., whole grain bread) are digested slowly, so they do not trigger dramatic fluctuations in blood glucose and insulin levels. As a result, we feel fuller, longer, and are less likely to overeat. The bottom line: whole grains and other low GI foods in your diet may reduce the risk of heart disease and Type 2 diabetes2.
The easiest way to eat lower glycemic foods is to choose foods that are also high in complex carbohydrates, such as whole grain breads or pasta, brown rice, beans, lentils, and fresh vegetables.
A word on fibre
The recommended amount of fibre is 25 grams per day for women, and 38 grams per day for men. Eating the amounts of whole grains, fruits and vegetables listed in Canada’s Food Guide to Healthy Eating will ensure an adequate fibre intake.
Be sure to choose from both water-soluble fibre (i.e., oatmeal, oat bran, barley and legumes) and water-insoluble fibre (i.e., wheat bran). Soluble fibre helps to control blood sugar and lower blood cholesterol; whereas, insoluble fibre helps to reduce the risk of constipation, and may reduce colon cancer.
According to Monica Gray, a Registered Dietician practising in Burlington, Ont.,,… “the easiest way to keep glucose and insulin levels in the normal range is to consume complex carbohydrates that are generally high in fibre and low on the glycemic index. For example, start the day with whole grain breads or high fibre cereals, and include beans or lentils with lunch or dinner.”
Losing weight and staying healthy
Health Canada recommends that carbohydrates should represent about 55 per cent of our total calories6. For optimum health, the scientific literature suggests choosing complex carbohydrates – food choices that are generally high in fibre and low on the GI — and limiting simple carbohydrates such as sugar, soft drinks and other foods with added sugar. Dr. Atkins was right to focus on carbohydrates – but he should have been more concerned with the quality, not the quantity, of carbohydrates in the diet.
Donna Shaw is a food and nutrition marketing professional with a focus on the communication and promotion of healthful food to the growing number of health-conscious consumers. She has a B.Sc. in Nutrition, an MBA in Agribusiness and over 20 years of marketing experience. Donna can be reach at by e-mail at: email@example.com.
1. Atkins, R.C. Dr. Atkins’ new diet revolution. New York: Simon & Schuster, 1998.
2. Thompson, J., Manore, M., and Sheeshka, J. Nutrition: A Functional Approach. Toronto: Pearson, 2005.
3. Lean, M.E.J., and Lara, J. Is Atkins dead (again)? Nutrition Metabolism and Cardiovascular Disease (2004) 14: 61-65.
4. Astrup, A., et al. Atkins and other low-carbohydrate diets: hoax or an effective tool for weight loss? Lancet (2004); 364: 897-99.
5. Harvard Health Letter (2003). Volume 23; 7.
6. Health Canada website www.healthcanada.com.
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