The Carbohydrate Conundrum
Although the long-term effectiveness remains to be proven, a large percentage of the population, in some surveys as much as 25%, claims to be watching its carbohydrate intake. Thus, people have been led to believe that highly nutritious, carbohydrate-based foods such as carrots, oatmeal and other cereals are culpable causes of fatness. They also believe that expunging these foods is the key to a sylph-like self. To add to the misconceptions, advertising campaigns are touting high fat, deep fried entrées as being low-carb and somewhat healthful.
This diet paradigm is in stark contrast with a body of knowledge showing that diets with carbohydrates impart health benefits and help with weight maintenance. For instance, an analysis of the diets of 600 children, aged 4-12 years old, demonstrated that children who normally ingest eight or more servings of ready-to-eat cereal in 14 days, were 75% less likely to be overweight than those who consumed three or fewer servings of cereal. Half of the children who were in the group that seldom ate cereal were overweight. This study included all types of cereal, such as whole grain and pre-sweetened cereals. Frequent cereal eaters also were shown to consume less fat and cholesterol and more vitamin A, calcium, iron, zinc, and several B vitamins.4 Similar results were shown in a study of over 74,000 middle-aged women. Those who ate more fiber-rich grains—such as oatmeal and whole-grain breakfast cereals—gained less weight over the 12 years of the study than did women who ingested the least amount of fiber. Also, they were half as likely as those with the lowest intake to become obese.5 The opposite was true if the diets were heavy in refined-grain products like white bread and pasta.
Similarly, in 10,014 U.S. adults over the age of 19, the quartile ingesting the most carbohydrate (55%) were more likely to have normal body weights (BMI <25) than the quartiles ingesting either very low, low, or moderate carbohydrate. Further, they were more likely to meet nutrient recommendations, and to eat a higher volume of food per 1000Kcal.6,7
Why the Conundrum?Why does certain research support the effectiveness of low-carb diets? First, strategies for maintaining or not gaining weight are not the same as for losing weight. This is especially true for very overweight individuals where metabolic changes—including high levels of circulating insulin—make losing weight difficult. Second, consumers tend to paint all carbohydrates with the same brush. Thus, we see consumers not eating carrots and oatmeal, which may well be a wrong-headed strategy.
Research suggests that, when it comes to weight control, whole grains such as oats, bran and brown rice have an advantage over highly processed, low-fiber grain products. Fiber-rich whole grains are more filling, and data on people who favor them over refined grains suggest they are more likely to have a normal body weight. There are several reasons for this. Carbohydrates from foods such as whole grains may contain viscous fibers and slow-release and resistant starches that may modulate levels of sugar in the bloodstream. These foods also may contain phytochemicals and enzyme inhibitors.
All these can alter some metabolic reactions and decrease fat storage or may reduce the number of calories available to the body. Consumers have a terrible time just trying to understand what a carbohydrate is—much less being able to differentiate between carbohydrates that contribute more than just calories and provide little in the way of nutrition or satiety, and those that enhance satiety and make important dietary contributions.
Third, many diet books and consumers fail to understand that glycemic index values are based on equal amounts of available carbohydrate (50g of carbohydrate), not equal amounts of food. For instance, take the poor carrot, which is said to have a high glycemic index. While this is true, the glycemic index of the carrot is high compared on 50g carbohydrate. However, most books fail to state that seven servings of carrots must be eaten to get 50g of carbohydrate.
Those in the National Weight Control Registry, (called Successful Losers) have lost 50lbs. and have kept it off for at least a year. They adhere to the following practices: 1.) they exercise regularly, at least 30 minutes three times per week, 2.) they have a consistent weekly routine and 3.) they consume diets that are high in complex carbohydrates, fruits and vegetables, and moderate in fat.
2 Ebbeling CB, et al., 2003. A reduced-glycemic load diet in the treatment of adolescent obesity. Arch Pediatr Adolesc Med. 157(8):773-9
3 Foster GD, et al., 2003. A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med. 348 (21):2082-90
4 Albertson AM, et al., 2003. Ready-to-eat cereal consumption: Its relationship with BMI and nutrient intake of children aged 4 to 12 years. J Am Diet Assoc. 103(12):1613-9
5 Liu S, et al., 2003. Relation between changes in intakes of dietary fiber and grain products and changes in weight and development of obesity among middle-aged women. Am J Clin Nutr.; 78(5):920-7
6 Bowman SA and Spence JT. 2002. A comparison of low-carbohydrate vs. high-carbohydrate diets: energy restriction, nutrient quality and correlation to body mass index. J Am Coll Nutr. 21(3):268-74
7 Kennedy E., et al., 2001. Popular diets: correlation to health, nutrition and obesity. JADA. 101(4):411-20
Caption: Short-term studies have shown that low-carb or low-glycemic-carbohydrate food diets with high saturated fats help people quickly lose weight.
Caption: Foods based on fiber-rich whole grains often contain viscous fibers and slowly released and/or resistant starches that may modulate levels of sugar in the bloodstream.