Copyright © 2009
by Daniel Matthew Korn

All Rights Reserved

If fats do not necessarily cause weight gain, another culprit must be the cause. The theory that carbohydrates cause weight gain and loss of blood sugar control was popularized by Dr. Robert Atkins. There are now many diets advocating reducing or eliminating certain kinds of carbohydrates, as did his diet. There is little debate that refined grains and refined sugars are unhealthful, but some people believe these carbohydrates in their unrefined forms are unhealthful as well and are responsible for obesity.

Carbohydrates fill numerous roles in living organisms. They are involved in the storage and transportation of energy, they are used to build cartilage in animals, and they play a role in the immune system, fertilization, and blood clotting. The reason people can live on high fat diets like that devised by Dr. Atkins is because humans have the ability to make the carbohydrate glucose out of protein and fat.¹ The brain and nervous system require glucose to function properly.

Clearly, we cannot say that all carbohydrates are bad or even that all sugars are bad. The body requires sugars to survive, even manufacturing them when they are not consumed. That having been said, the carbohydrates we eat today are different from those we ate historically. Today we are processing, or refining, grains with machinery that removes many of their components, enabling the production of non-whole grain foods like white bread, white rice, and pasta and baked goods made with white flour. Most of what we call whole wheat, but not 100% whole wheat, has been changed nutritionally as well. Processing increases the speed with which food raises blood sugar and decreases its nutrient quantity. Refined grains that have a lower nutrient content are certainly less healthful than whole grains, but the exact mechanism by which this could be related to obesity is disputed.

There are scientists who believe that, by eating more foods that quickly raise our blood sugar, we are harming our bodies’ ability to properly lower our blood sugar after meals, and raised blood sugar is a symptom of obesity. Their theory is that weight gain and loss of blood sugar control are caused by the body’s reaction to these sharp changes in blood sugar, and that the key to weight loss is to avoid foods that cause rapid increases in blood sugar. This idea is still controversial among scientists.² It is widely claimed, and experiments confirm, that diets low in refined carbohydrates and sugars help people achieve weight loss, but it does not appear that consumption of refined carbohydrates causes blood sugar control problems or obesity in all circumstances. To demonstrate this, let us see whether all populations which eat a diet high in refined carbohydrates develop obesity.

Thai meals always include rice. The Thai term for something served with rice literally means “not rice.” In the 1950s, a group of researchers from Cornell University studied the diet of a small rice-growing village. They found that both the rich and the poor got about 80% of their calories from rice. Almost all of this rice was processed white rice, a refined carbohydrate. The remaining calories came chiefly from unrefined carbohydrates, mostly fruits and vegetables. The main health problems the villagers experienced were a deficiency of vitamin B1, which is naturally present in rice but is removed by processing, and parasitic infections due to poor sanitary conditions. Neither starvation nor obesity was mentioned as a health concern.³

At the national level in Thailand, consumption of white rice, a refined carbohydrate, still makes up between 70% and 80% of the calories in the diet.⁴ In the United States, calories from carbohydrates make up about 50% of the diet.⁵ The percentage of Thai adults who are obese (BMI ≥ 30) is less than 6%.⁶ This is more than 80% less than the rate in the United States and a far lower rate than that of any European country. More interestingly since genetics can’t explain the difference, in Thailand the rate of obesity is highest in the urban areas. There nutrition is more similar to the Western diet; consumption of refined carbohydrates is lower than in the rural areas. Since obesity in Thailand is highest where consumption of refined carbohydrates is lowest, refined carbohydrates, at least in the form of white rice, cannot be the cause of obesity in that country.

The lack of obesity in rural Thailand is surprising, because refined carbohydrates have been linked to weight gain. There are several possible reasons why the rural Thai are not gaining weight despite the high amounts of refined carbohydrates in their diet. The rural Thai consume a diet which is very high in nutrients and fiber in the form of fruits and vegetables, and this may counteract the lack of nutrients and fiber in white rice. Also, the fat soluble nutrients in rice bran and germ may help prevent obesity. Although the bran and germ of the rice kernel are removed during refining, they are fed to chickens, leaving the fat soluble vitamins in the food supply. Whereas excess fat soluble vitamins can be stored in chicken fat, water soluble vitamins cannot be preserved in the same manner. The rural Thai were found to be deficient in vitamin B1, and this is a water soluble vitamin. Later, we will look at the evidence that one of the fat soluble nutrients is helping to prevent the rural Thai from gaining weight, despite a diet high in refined carbohydrates. Thailand’s very low prevalence of obesity despite high consumption of refined carbohydrates is not unique. In Bangladesh, where over 70% of calories come from white rice, the prevalence of obesity is about 1%.^7,8

While fruit juice is filled with many nutrients, calorically it is almost pure sugar. For this reason, people who believe that sugar is responsible for obesity and loss of blood sugar control discourage the drinking of fruit juice. In 2006, the Minnesota Medical Association asked the federal government to remove fruit juices from its subsidized meal program that serves about 8 million low-income Americans.⁹

However, we should recognize that fruit juice was available long before the modern period. The Greeks fermented grapes to make wine, and certain Zoroastrian Persians ate a diet that consisted almost completely of fruit and fruit juice.¹⁰ Despite the fact that fruits and fruit juices have been consumed for thousands of years, until the twentieth century there was no example of a society in which even one percent of the population was obese. Not surprisingly, in the same year the Minnesota Medical Association made its request to the federal government, a study was published showing no correlation between consumption of pure fruit juice and weight gain.¹¹ Other studies have reached similar conclusions.¹²

Over the last forty years, during a period of dramatically rising obesity, Americans have been getting more of their calories from refined sugar. While the two factors are correlated, it does not appear that sugar directly causes obesity or the associated loss of blood sugar control. In addition to the previous examples, a three-year study published in 2002 by the National Academy of Sciences concluded, “There is no clear and consistent association between increased intake of added sugars and [body weight].”¹³

Low carbohydrate diets replace refined carbohydrates with fruits and vegetables. Eating more fruits and vegetables has been shown to lower body weight.¹⁴ However, decreased consumption of fruits and vegetables and increased consumption of flour cannot be the complete cause of obesity. In the United States from 1909 to 1965, consumption of fruits and vegetables rose while consumption of flour and cereal products fell. Consumption of meat, poultry, dairy, and fish also increased.¹⁵

In 1996, the amount of flour and cereal products consumed in the United States per person was 100 pounds below the 1909 level. Proponents of low carbohydrate diets point out that consumption of cereal and wheat products has been increasing since the 1970s, but they generally do not mention that there has been a net decrease in such consumption of more than a third since 1909. It is estimated that the consumption of wheat and other cereals was much higher before 1909.¹⁶ During the period from 1909 to 1996 obesity skyrocketed, despite a move towards a diet that was lower in flour and other grain products.¹⁷

Carbohydrate avoidance can help reduce blood sugar, which is one reason why low carbohydrate diets cause weight loss. Blood sugar that is low, even if it is still in the normal range, is a signal for the body to use stored fat. However, carbohydrate consumption is not responsible for poor blood sugar control or obesity. The high refined carbohydrate American diet is associated with weight gain, yet the high refined carbohydrate diets of Thailand and Bangladesh are not. Though low carbohydrate diets have had some success in achieving weight loss, this comparison demonstrates that the theory explaining their effectiveness cannot be correct.

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Citations:

¹ "Is dietary carbohydrate essential for human nutrition?" - Westman 75 (5): 951 - American Journal of Clinical Nutrition

³ Hauck, Hazel M. et al, Food Habits and Nutrient Intakes in a Siamese Rice Village, Studies in Bang Chan, Cornell University, Ithaca, New York, 1958

⁴ Gershoff, Stanley N. "Amino acid fortification of rice studies in Thailand." The American Journal of Clinical Nutrition. 4/04/2009 http://www.ajcn.org/cgi/reprint/28/2/170.pdf.

⁵ "National Health and Nutrition Examination Survey." National Center for Health Statistics. 4/04/2009 http://www.cdc.gov/nchs/nhanes.htm.

⁶ Pongchaiyakul, C. "Defining obesity by body mass index in the Thai population: an epidemiologic study." PubMed. 4/04/2009 http://www.ncbi.nlm.nih.gov/pubmed/16837420.

⁷ "Rice and human nutrition." Food and Agriculture Organization of the United Nations. 8/09/2009 http://www.fao.org/rice2004/en/f-sheet/factsheet3.pdf.

⁸ "WHI Global InfoBase: Bangladesh: All Data." World Health Organization. 8/09/2009 http://apps.who.int/infobase/reportviewer.aspx?rptcode=ALL&uncode=50&dm=5&surveycode=200021a1&print=1.

⁹ Lerner, Maura. "Fruit juice is a target in the war on obesity." Star Tribune. 4/04/2009 http://www.startribune.com/lifestyle/health/11345236.html.

¹⁰ "History of Iran." Iran Chamber Society. 4/04/2009 http://www.iranchamber.com/history/articles/sassanids_religious_turmoil.php.

¹¹ Nicklas, Theresa A. "Association Between 100% Juice Consumption and Nutrient Intake and Weight of Children Aged 2 to 11 Years." Archives of Pediatrics & Adolescent Medicine. 4/04/2009 http://archpedi.ama-assn.org/cgi/content/abstract/162/6/557.

¹² "Drinking juice not associated with overweight and obesity in children." News-Medical.Net. 4/04/2009 http://www.news-medical.net/?id=38842.

¹³ Dietary Reference Intakes. Washington, D.C.: National Academies Press, 2004. p. 96

¹⁴ Leonard H. Epstein and others. "Increasing Fruit and Vegetable Intake and Decreasing Fat and Sugar Intake in Families at Risk for Childhood Obesity." Obesity: A Research Journal. 6/04/2009 http://www.nature.com/oby/journal/v9/n3/full/oby200118a.html.

¹⁵ Willis A. Gortner. "Nutrition in the United States." American Association for Cancer Research. 6/04/2009 http://cancerres.aacrjournals.org/cgi/reprint/35/11_Part_2/3246.pdf.

¹⁶ Hans Diehl. "Western Diet Food Not Nutritious and High Calorie." Coronary Health Improvement Project. 6/04/2009 http://www.chiphealth.com/topics/diet-01-western-diet-changed.html>.

¹⁷ "Agriculture FACT BOOK 98: Chapter 1-A." United States Department of Agriculture. 6/04/2009 http://www.usda.gov/news/pubs/fbook98/ch1a.htm.