A few weeks ago I posted a piece on weight maintenance in which I pointed out that James O. Hill, Ph.D., a researcher from the University of Colorado who seems to be the go-to guy when anyone from the media wants a quote against the low-carb diet, had written a white paper for the sugar lobby. I had stumbled into this white paper a few years earlier when I had clicked on to the sugar lobby’s website. I couldn’t believe at the time that a serious academic nutritional research scientist would write such a thing, even for pay. But there it was for all to see.
When I was writing the above mentioned post I searched for the white paper on the sugar lobby website, but it was no longer there. I then did a Google search and found it listed at the top of the Google list, but when I clicked on, there was no paper. The page had been removed. I then noticed that there was a cached copy, and when I clicked on, there was the white paper.
I got an email from a colleague who had read this blog post and had tried the links I had provided and had come up empty. He was wondering if I had not put up the correct links. I reran the Google search and found that using the same search words I had used before — james o. hill white paper sugar — got me nowhere, whereas previously these same words took me to the cached version of the paper. I tried searching every way possible, but found no link to the white paper. I can’t imagine who removed it.
Fortunately, when I found it previously I copied the entire thing. And since the outfit funding the paper, the sugar lobby, figured that the white paper would do nothing but promote the use of sugar, they gave permission for anyone to reprint it.
So, here it is in its entirety save a couple of graphs that didn’t pick up when I copied it.
The Role of Carbohydrates in Weight Management
James O. Hill, Ph.D., University of Colorado Health Sciences Center
Obesity is a serious, but preventable, U.S. health problem. Diet and lack of physical activity are the two most important controllable factors behind the alarming increase in overweight and obesity. While there is little disagreement over the importance of physical activity in weight loss and weight maintenance, there is a lack of consensus regarding diet. Theories abound as to which dietary component most contributes to weight gain. One popular theory indicts sugar and points to foods with a high-glycemic index. However, the theory that dietary sugar equals high insulin levels equals excess fat deposits is unproven and makes little biological sense. In fact, sugar has a glycemic index similar to most starches. The bottom line is that sugar and sugary foods do not promote weight gain when they are eaten in amounts that do not exceed calorie needs. Neither do they contribute to the development of diabetes. Experts now agree that sugar is not uniquely problematic, even for diabetics. The fact remains that weight management is still an issue of positive energy balanceâ€”too many calories, consumed from any source, and not enough burned off results in weight gain. A high-carbohydrate, low-fat diet coupled with regular physical activity remains the best advice for weight loss and weight maintenance, as well as for overall good health.
The purpose of this paper is to address the role of carbohydrates, especially sugar, in weight management.
Obesity is a serious health problem in the United States, having reached epidemic proportions. It now ranks second only to smoking as the leading cause of preventable death in the U.S. Being overweight or obese increases the risk of hypertension, elevated cholesterol, type 2 diabetes, coronary heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea and respiratory problems as well as endometrial, breast, prostate and colon cancers.
The recently concluded third National Health and Nutrition Examination Survey (NHANES III) found that the majority (55%) of adults in the U.S. are overweight and many (22%) are obese, amounting to an estimated 97 million adults. There has been an especially large increase in obesity over the last 20 years. Most disturbing is the increase in the incidence of overweight among children. NHANES III found a higher proportion of overweight children than in previous surveys.
Overweight in adults is generally defined as a body mass index (BMI) of 25.0 to 29.9 and obesity as a BMI of 30.0 or greater. (BMI is a measurement of body fat relative to height, and is closely related to a person’s total body fat.) As the BMI increases over 30.0, the related health risks rise. A BMI of 35.0 or greater reflects morbid obesity and is clearly associated with increased risk of type 2 diabetes, cardiovascular disease and other obesity- associated conditions. For children, many researchers believe that concern about overweight should begin at the 85th age-specific percentile of BMI. Using this standard, about 25% of children in the U.S. are considered overweight. About 30% of children who are obese become obese adults. And an obese child who becomes an obese adult is likely to have more severe adult obesity than adults whose obesity begins in adulthood. Because obesity is defined as excess body fat, BMI technically defines overweight and not obesity. However, the two terms are often used interchangeably.
Although obesity has a clear genetic component, the country’s gene pool has remained essentially unchanged in the last few decades, pointing to environmental and behavioral factors as being the largest contributors to the growing problem. Diet and lack of regular sustained physical activity are the two most likely candidates. However, the most heated dietary debate is over the role diet composition (particularly fat and carbohydrate) plays in weight management.
On one side of the argument are experts who say excess calories, regardless of source, are the culprits. Others, however, point to excess calories from fat or carbohydrates, particularly sugar, as being responsible for weight gain. But while few studies have made distinctions among the different kinds of carbohydrates, several studies have found a strong relationship between excess fat intake and obesity. However, not everyone agrees that fat plays such a pivotal role.
One factor, for which there is virtually unanimous agreement is physical activity. An increase in routine physical activity is an important component of weight loss and an even more critical factor in long-term weight maintenance.
Adult Body Mass Index
Health risk based solely on BMI: dark gray = moderate to extremely high, light gray = low, white = minimal
Carbohydrates can be divided into three main groups, sugars (monosaccharides, disaccharides and polyols), oligosaccharides (maltooligosaccharides and other oligosaccharides) and polysaccharides (starch and nonstarch polysaccharides such as cellulose and pectin). “Sugars” typically refer to monosaccharides (a sugar such as glucose or fructose that can not be broken down to a simpler form) and disaccharides (sugars, such as sucroseâ€”table sugarâ€”that can be broken down into two monosaccharides). Glucose, fructose and sucrose are found naturally in fruits and vegetables. Sucrose, or table sugar, the disaccharide most commonly consumed by vegetarians and nonvegetarians alike, is made up of both glucose and fructose. Lactose, the sugar found in milk and dairy products, is the other most commonly consumed disaccharide.
Starch is the primary polysaccharide of plants and the most abundant carbohydrate found in food. The term “complex carbohydrates” was coined as a nutritional concept to signify both starches and dietary fibers. Insoluble fibers such as cellulose and hemicellulose, which are found in vegetables and whole grains, form the cell walls of plants. They bind water, increase fecal bulk and speed the passage of food through the digestive tract. Water-soluble fibers, such as pectin and beta-glucan, swell in water to form viscous, gel-like substances that slow absorption through the wall of the small intestine. Most soluble fibers are fermented to some degree by bacteria in the large intestine and are associated with lowered blood cholesterol and blood glucose.
All digestible carbohydrates, no matter their original form, are broken down into monosaccharides in the mouth, stomach and small intestine before entering the bloodstream. During digestion, sucrose is converted into equal parts of its componentsâ€”glucose and fructoseâ€”which enter the bloodstream through the walls of the small intestine. The blood delivers glucose and fructose to the liver.
Glucose that is needed to meet immediate energy demands passes through the liver and back into the blood, continuing its journey to the cells. Most excess glucose is converted and stored in the liver as glycogen, a starch-like compound. Fructose is metabolized in the liver and converted to compounds used to produce glycogen. Since fructose is transformed into glycogen, very little fructose is actually found in the blood.
When the body needs more energy, the liver converts glycogen back into glucose, which is then delivered by the bloodstream to the brain, muscle or other organs. Body cells break down blood sugar (glucose) into carbon dioxide and water, and energy is released.
In a normal person, the glucose level in the blood rises within 30 to 60 minutes after eating. The pancreas responds by producing the hormone insulin, which lowers the blood sugar level by helping glucose enter the cells. Individual carbohydrate foods vary greatly in their effects on blood sugar. Some starchy carbohydrate foods, such as white bread, give a very rapid blood sugar response, while others, such as whole grain spaghetti, produce a slower rise. Sugar has a moderate effect on blood sugar and blood insulin.
The Glycemic Index, Insulin Resistance and Overweight
Several articles in the popular press have promoted the theory that the growing prevalence of obesity in the U.S. is the result of increased blood glucose and insulin levels caused by the consumption of high-carbohydrate diets. According to this theory, diets high in total carbohydrate, especially ones that contain a large percentage of foods whose glycemic indexes approximate those of white bread and instant rice, lead to increased insulin levels, particularly in the 25% of the population believed to be insulin resistant. (Glycemic index is a way of measuring blood glucose response to a standard amount of a single, specific food. Insulin responses generally follow the same rank order of the glycemic responses, with the exception of protein foods which elicit an insulin response without an accompanying glycemic response.) This is purported to lead to an increased conversion of “excess” carbohydrates to body fat. There are several reasons why this theory, which sounds plausible at first, does not make biological sense.
First, the glycemic index was never intended to be used alone. It is merely one additional tool for researchers to use when studying the effects different foods have on blood sugar and insulin levels. It was certainly not developed to be used as a guide to which foods are most fattening. Second, it takes an extraordinary excess of carbohydrate to produce fat, and even then, very little net fat is produced from carbohydrate. Third, the idea that people with insulin resistance are particularly prone to obesity when eating high-carbohydrate diets is unsubstantiated by scientific evidence. Diets high in carbohydrates, including sugar, simply do not promote weight gain when they are consumed in amounts that do not exceed energy requirements. And last, researchers now believe that insulin resistance is caused by insulin receptors that don’t respond properly, not by too many carbohydrates in the diet. The receptors’ inability to respond to insulin is aggravated in people who are overweight or obese, more evidence supporting the positive effects of sustained, routine physical activity.
Experts recognize that sugar is not uniquely problematic, even for diabetics. For most of this century, the most widely held belief about the treatment of diabetes was that sugars should be avoided and replaced with “complex carbohydrates.” The belief was based on the assumption that sugars are more rapidly digested and absorbed than are starches, thereby aggravating elevated blood sugar to a greater degree. That belief has persisted in the minds of consumers and scientists alike. However, according to the American Diabetes Association, there is very little scientific data to support this notion. Fruits and milk have been shown to have a lower glycemic response than most starches, and sucrose produces a glycemic response similar to that of rye bread, brown rice and sweet potatoes. And sweetened breakfast cereals often have a lower glycemic index than do some nonsweetened cereals.
The ideal amount of sugars to be included in the diet is not known. However, avoidance of sugar is not necessary for blood glucose control and is not advised because it may actually result in increased intakes of fat and starches with high-glycemic indexes. In fact, the American Diabetes Association now states that the use of sucrose as part of a meal plan does not impair blood glucose control in people with diabetes and may be substituted for other carbohydrates, as long as it is not added to the total carbohydrate already allowed.
It may be true that prolonged high blood glucose and insulin responses following food intake may promote development of glucose intolerance, a forerunner of type 2 diabetes, but since most cooked or refined starchy foods produce higher blood glucose and insulin responses than sucrose, this does not indict sugar or the other carbohydrate sweeteners as a causative factor. There is no evidence that sucrose causes a deterioration of blood glucose control in the long term, nor is there any evidence that sucrose causes excess insulin secretion, predisposing people to diabetes. Excess calories, whether from protein, fat or carbohydrate, that result in weight gain do, however, increase the risk for developing type 2 diabetes.
While there is no evidence that carbohydrates in general or sugar in particular affect insulin resistance or the development of type 2 diabetes, increased physical activity coupled with weight loss have been proven to improve insulin resistance and lower the risk of developing type 2 diabetes, as well as the health risks that typically accompany it over the long term.
Are All Calories Created Equal?
Despite the widely held belief that “a calorie is a calorie” a number of studies suggest that, in the short-term, all calories are not equal and that excess calories from a high-fat diet play a unique role in weight gain. Research shows that when similar levels of excess calories (normalized to baseline energy requirements) are consumed, more body fat is gained when a high-fat diet is eaten than when the excess calories come from a low-fat, high-carbohydrate diet. This apparent anomaly occurs because there is an oxidation hierarchy of metabolic fuels (protein > carbohydrate > fat).
Excess dietary fat is more likely to be stored as body fat, and with greater efficiency, than excess protein or carbohydrate. Specifically, short-term carbohydrate overfeeding produces progressive and rapid increases in carbohydrate oxidation whereas short-term fat over-feeding has little effect on fat oxidation. Only 75% to 85% of excess carbohydrate calories, compared to 90% to 95% of excess fat calories, are stored as body fat.
The more prolonged the overfeeding, the less the difference between carbohydrate and fat calories. The oxidative difference between excess carbohydrate and fat calories peaks during the first seven days of overfeeding.
Whichever theory applies to the development of obesity, balancing energy intakes and expenditures is mandatory. Increased physical activity is the key to achieving this balance.
Influence of Sugar Intake on Total Food Intake and Obesity
The liking for sweet taste begins at birth and is thought to be innate. Although there is little evidence that sugar itself contributes to excessive food intake and obesity, sugar increases the palatability of foods and is often associated with fat in foods, which is associated with obesity. Evidence for a positive relationship between dietary fat and body weight is found in epidemiologic and observational studies, animal feeding trials and short-term interventions. Moreover, there are very few populations around the world who eat a low-fat diet and have a significant problem with obesity, a finding that supports the suggestion that consumption of low-fat diets may be protective, while high-fat diets may promote obesity. Estimates of food intake in a group of people from the National Weight Control Registry who had successfully maintained weight loss led to the conclusion that consumption of a low-fat diet (approximately 20% of energy from fat) along with regular physical activity is the key to long- term weight maintenance.Contrary to many people’s belief that sugar contributes to obesity, research has found that groups consuming the most sugar actually have the lowest levels of obesity. This is most likely because of the “fat-sugar see-saw.” That is, as sugar intake goes up, fat intake goes down. Due to differences in levels of physical activity coupled with inherent genetic variability, it is well recognized that some people are more susceptible to weight gain while eating high-fat diets. Moreover, the major impact of reducing fat intake may not be in reversing obesity, but in preventing weight gain in the first place.The regulation of food intake is thought to be the main difference between carbohydrate and fat. There is considerable experimental evidence that high-fat, high-energy diets undermine the weight regulatory systems of humans and promote obesity. In contrast, high-carbohydrate diets don’t seem to have the same disruptive effect on weight regulation, and in this respect, these lower energy dense diets seem to have a useful role in the long-term prevention of obesity.
Some research also suggests that despite the widely held beliefs that fat is more satiating than carbohydrates, and that carbohydrates, especially sugar, trigger overeating, carbohydrates may actually regulate appetite better than fat. One study found that when a premeal feeding was given as carbohydrate, caloric intake was balanced over the rest of the day so that there was no significant difference in overall energy intake between the low- and high- calorie premeal feedings or controls. On the other hand, when the excess calories were provided as fat, the total intake over the day was significantly higher because of a failure to compensate for the additional calories. Studies looking specifically at sugar have found that a premeal drink or snack containing sugar did not suppress appetite, but neither did it trigger overeating.
High-fat diets can easily result in the unintentional overconsumption of calories. The opposite appears to be true for carbohydrates. Even in studies in which the goal is to maintain a constant energy intake, energy intake often is reduced unintentionally when a low-fat diet, high-carbohydrate diet is consumed. Moreover, there is no evidence to support the suggestion that sugar is unique among dietary carbohydrates as an appetite stimulant.
Still, the theory that sugar is somehow uniquely fattening persists. Carbohydrates, including sugar, were blamed when data from NHANES III showed that while the percentage of fat in Americans’ diets was dropping, obesity was on the rise. This apparent anomaly led to the popularized conclusion that lower-fat, higher-carbohydrate diets led to increased insulin levels, particularly in insulin-resistant people, causing the increased amount of carbohydrate to be stored as fat. However, a closer look at the NHANES III data revealed that while fat as a percent of total caloric intake dropped from the NHANES II survey, the absolute amount of fat consumed had not changed. The drop in percent calories from fat resulted simply because total calories had increased. And in fact, it has been suggested that fat intake may be even higher than dietary surveys such as NHANES find, since many people underreport fat consumption because of its negative health connotations.
A recent study provides further evidence that sugar is not uniquely fattening. A group of sixty women who were 130% to 200% of their ideal body weight were given either high- or low-sucrose, low-fat, reduced-calorie diets as a part of a six-week weight-loss program. The researchers found that a high intake of sucrose did not adversely affect weight loss when compared with a diet in which sucrose was replaced by starches and the artificial sweetener aspartame. Both groups showed equally significant reductions in weight and percentage body fat.
Food and Taste Preferences and Weight
Although a preference for sweet taste does not account for obesity, preference for fat may be a factor. Research shows that obese individuals prefer the same concentration of sugar but higher concentrations of fat than normal- weight individuals. Obese women generally prefer fat-sweet combinations, particularly desserts, whereas obese men prefer the salt-fat taste of high-protein, high-fat meats and high-fat, salty snacks. It is often overlooked that sugar is not the main source of energy in many popular sweet foods; chocolate, cookies, cake, ice cream, and sweetened dairy drinks derive most of their calories from fat. If you consider that the obese seem to be less able than normal weight individuals to respond to internal cues to stop eating, it makes sense that eating fat-sweet foods, especially for obese women could lead to overeating. Since most fat-sweet foods also contain other types of carbohydrate, it is difficult to target sugar as an overeating trigger. There is no research describing the effect of sucrose on appetite compared to carbohydrates that are not sweet.
A review of the effect of sugar on appetite found that there was no consistent evidence to label sugar as an appetite stimulant, thereby contributing to excess caloric intake and obesity. Some studies report appetite suppression, while others show appetite stimulation or no appetite effect. Because most of the studies were short- termâ€”five days or lessâ€”they may not be appropriate for testing the effect of any particular food or nutrient on appetite. Research shows that although individual food intakes vary by about 30% from day to day, body weight remains stable. This suggests that body weight regulation is achieved through long-term, not-short term adjustments in food intake, rendering such short-term studies relatively meaningless.
Eating Healthfully for Weight Management
A high-carbohydrate (55% to 60% of calories), low-fat (20% to 25% of calories) diet remains the best recommendation for weight loss and weight maintenance as well as for overall healthful eating. A high- carbohydrate diet appears to reduce the likelihood of overeating, rather than increasing it, as some popular diet theories purport. And if overeating does occur on a high-carbohydrate diet, it is slightly less likely to be stored as body fat. Moreover, the inclusion of sucrose in a high-carbohydrate diet does not increase the likelihood of weight gain or the development of glucose intolerance or diabetes.Also critical to a healthful weight-management diet is the inclusion of five to nine servings of fruits and vegetables a day. Study after study clearly indicate a positive relationship between consumption of fruits and vegetables and a lower incidence of several diseases including cancer, heart disease and high blood pressure. They are good sources of fiber, which may play a role in controlling weight, regulating blood sugar, lowering blood cholesterol and preventing constipation. And they provide a vast array of phytochemicals, naturally occurring plant compounds that researchers believe play an important role in disease prevention.
Bridging the Gap with Physical Activity
Obesity is ultimately an issue of long-term positive energy balance, with too many calories consumed and not enough burned off, and occurs regardless of the source of the excess calories. Energy balance is determined not by diet or activity alone, but by the interaction between the two. Inactivity contributes to an energy imbalance that leads to weight gain and, if left unchecked, obesity and its accompanying health risks. In fact, the transition to a habitually sedentary lifestyle has been identified as the major contributor to the growing obesity rate in both the U.S. and the UK. Not only does regular physical activity reduce the risk of obesity, it also lowers coronary disease risk factors, including high blood pressure and elevated triglycerides, increases HDL-cholesterol and improves glucose tolerance with or without weight loss. Research suggests it may also reduce the risk of some kinds of cancer. In 1998, an expert panel recommended that all adults set a long-term goal to accumulate at least 30 minutes of moderate-intensity physical activity on most, and preferably all, days of the week. However, the 1996 Surgeon General’s Report on Physical Activity found that 60% of American adults are not regularly active and that 25% engage in no activity at all. Inactivity is a growing problem in children and adolescents as well. Only about one-half of young people ages 12 to 21 years regularly participate in vigorous physical activity. One-fourth report no vigorous activity at all. Some of the increase in inactivity has been blamed on television. One study found that in a group of 10 to 15 year olds, the odds of being overweight were 4.6 times greater among those who watched more than five hours of television a day, compared to those who watched two hours a day or less. The appeal of television, electronic games and computers has increased the time spent in sedentary pursuits among children and adults alike.
Years of research has uncovered several important aspects of a combined aerobic and resistance exercise program in relation to weight management.
1. It promotes fat loss while preserving or increasing muscle mass.
2. Although the rate of weight loss resulting from increased physical activity without reduced calories is relatively slow, the combination of increased physical activity and reduced calorie intake appears to be more effective for long-term weight regulation than is dieting alone.
3. Reducing the risk of regaining lost weight, or minimizing weight gain in the first place, is directly related to the frequency and duration of exercise.
4. A reduced-fat diet markedly improves the potential of physical activity to achieve a negative energy balance.
5. Physical activity programs do not produce a compensatory increase in food intake in obese individuals.
6. Daily physical activity may assist weight loss by partially lessening the slow-down in metabolism that occurs during weight loss.
Funding for this paper was provided by The Sugar Association, Inc.
For copies, contact The Sugar Association, Inc., 1101 15th Street, NW, Suite 600 Washington, D.C. 20005 (202)785-1122.
This document may be reproduced without permission.