The Skinny on Sugar

With all the focus on weight in our society, it isn’t surprising that millions of people fall prey to fad diets and bogus weight-loss products.  Conflicting claims, testimonials, and hype by so-called “experts” can confuse even the most informed consumers.  One common trend with fad diets is that they restrict or completely eliminate certain foods.

should-i-quit-sugarThroughout the history of dieting and weight loss, many different foods have earned—both rightfully and wrongfully—their time in the spotlight, being vilified for America’s obesity problem and other chronic health issues.  From carb-restricted diets such as Atkins, Paleo, and Ketogenic, to low-fat diets such as Ornish, Pritikin, and 80-10-10, there is no shortage of restriction or elimination diets on the market.  It seems that every few years, there’s a new food bad guy in town.  The current public enemy No. 1?  Sugar.

In his book The Case Against Sugar, Gary Taubes claims that sugar is not only the root cause of today’s diabetes and obesity epidemics, but also is probably related to heart disease, hypertension, many common cancers, and Alzheimer’s.  Some experts have gone as far to declare that sugar is as addictive as cocaine and that it’s poisoning us.

One potential benefit of diets that reduce or eliminate sugar consumption is that they also reduce intake of many nutrient-poor foods, such as candy, soda, sugar-sweetened juice drinks, and other processed foods containing high-fructose corn syrup.  Much of the focus on sugar has been more specifically on high-fructose corn syrup, consumption of which has increased considerably in the past few decades.  Fructose has been shown to stimulate de novo lipogenesis (conversion of excess carbohydrates into fatty acids) and is associated with increases in liver fat, visceral adipose tissue, and serum triglyceride levels.  Robert Lustig, coauthor of “The toxic truth about sugar,” asserted that “a growing body of scientific evidence is showing that fructose can trigger processes that lead to liver toxicity and a host of other chronic diseases… a little is not a problem, but a lot kills.”1  But many studies show that the case against fructose and, more broadly, sugar, is greatly exaggerated.

Evidence showing that decreasing sugar consumption will reduce the prevalence of obesity is equivocal.  A meta-analysis of controlled feeding studies published in a 2012 issue of the Annals of Internal Medicine indicated that fructose has marginal effect on body weight, and only when ingested in extreme excess.2  The editors of the journal wrote that, “pure fructose had no effect on weight compared to diets that provided the same calories using non-fructose carbohydrate.”

A study that examined sugar consumption at levels representative of the American diet showed that both fructose and non-fructose sugar intake were unrelated with indicators of obesity, such as BMI and waist circumference.3  In some instances, the data actually showed a negative association—body weight tended to be lower with higher consumption of sugar.  With respect to other bio-measurements, increased sugar consumption was also inversely correlated with blood pressure, blood HbA1c concentration, and serum uric acid concentration.  High HbA1c levels can indicate prediabetes or diabetes, while high levels of uric acid can lead to gout, kidney stones, or kidney failure.  Further, a meta-analysis of studies attempting to reduce consumption of sugar-sweetened beverages showed an equivocal effect on body weight in all subjects.4

It’s standard for low-carb diets to advise reducing added sugars and limiting refined carbohydrate consumption.  Some diets, however, have upped the ante and called for the elimination of sugar altogether—both added and natural.  For example, the “I Quit Sugar” diet recommends cutting out all fruit to break your sugar addiction and to allow your body to “recalibrate” before reincorporating low-fructose fruit back into your diet.  Most fruits are not allowed under the standard ketogenic diet.  Keto advises against intake of tomatoes, peppers, berries, and citrus, while also suggesting complete avoidance of large, starchy fruits.  Similarly, the Sugar Busters Diet allows consumption of fruits with low sugar content, but it forbids high-glycemic fruit such as bananas, pineapples, apples, and pomegranates.

There is overwhelming epidemiological evidence that diets rich in fruit and vegetables are associated with reduced risks of cancer, heart disease, and other degenerative diseases.5  Plant-based foods, such as fruit, vegetables, and whole grains, which contain significant amounts of bioactive phytochemicals, may provide desirable health benefits beyond basic nutrition to reduce the risk of chronic diseases.6  Additionally, evidence suggests that an increased consumption of vegetables and fruit may prevent weight gain.7

Another concern with sugar elimination is that fiber intake is reduced as a result of cutting fruits and certain vegetables from one’s diet.  Dietary fiber is found naturally in fruits, vegetables, and whole grains, and it contributes to colonic health, coronary artery health, cholesterol reduction, glucose metabolism, insulin response, and blood lipid levels.8  Fiber is also beneficial for weight control because foods high in fiber contain fewer calories per weight and may reduce caloric intake by displacing high fat foods from one’s diet.9  Fiber also increases satiety and leads to feelings of fullness, which can prevent mindless snacking on empty calories.

The biggest problem with the anti-sugar campaign is that it vilifies only one aspect of an individual’s diet.  All macronutrients contribute to total energy intake, and concluding that sugar is obesogenic, but not fat or other complex starch, would be like pretending that, when eating a bag of M&M’s, only the green ones make you fat.

That sugar or carbohydrates in general are responsible for the development of obesity has been proposed in the past.  The proposal that insulin is key in favoring body fat gain is at the origin of numerous low-carb diets, Sugar Busters, and the Atkins Diet.  While these diets achieved significant, sometimes substantial short-term weight losses, they were associated with high rates of obesity relapse in the long term.10  Thus, while eliminating added sugars can be beneficial from a health standpoint, it is no guarantee of permanent weight loss.  Moreover, increases in circulating insulin levels are typically only observed when sugar is consumed in excess.  When sugar is consumed at levels equal to the median American intake, no changes in fasting insulin are observed, and insulin sensitivity is not changed.11  And, as mentioned above, in a nationally representative sample of the U.S. population, high intakes of sugar are associated with lower HbA1c levels—exactly opposite to what would be expected from popular opinion.

The bottom line?  It is the overall quality and quantity of our diet that matters to health—not just one villainous nutrient du jour.  There’s no need to intentionally target sugar as the culprit.  As long as you eat sufficient amounts of foods known to positively impact health, you can have your cake and eat it too.


1 Lustig RH, Schmidt LA, Brindis CD. Public health: The Toxic truth about sugar. Nature 2012;482(7383):27-9.
2 Sievenpiper JL, de Souza RJ, Mirrahimi A, et al. Effect of Fructose on Body Weight in Controlled Feeding Trials. Ann Intern Med 2012;156:291-304.
3 Sun SZ, Anderson GH, Flickinger BD, et al. Fructose and non-fructose sugar intakes in the US population and their associations with indicators of metabolic syndrome. Food and Chemical Toxicology 2011;49:2875-2882.
4 Kaiser KA, Shikany JM, Keating KD, et al. Will reducing sugar-sweetened beverage consumption reduce obesity? Evidence supporting conjecture is strong, but evidence when testing effect is weak. Obesity Reviews 2013;14:620-633.
5 National Academy of Sciences, Committee on Diet, Nutrition, and Cancer, Assembly of Life Sciences, National Research Council. Diet, nutrition, and cancer. Washington, DC: National Academy Press, 1982.
6 National Academy of Sciences, Committee on Diet and Health, National Research Council. Diet and health: implications for reducing chronic disease risk. Washington, DC: National Academy Press, 1989.
7 Boeing H, Bechthold A, Bub A, et al. Critical review: vegetables and fruit in the prevention of chronic diseases. Eur J Nutr 2012;51:637.
8 Prosky L. When is dietary fiber considered a functional food? Biofactors 2000;12(1-4):289-97.
9 Burton-Freeman B.  Dietary Fiber and Energy Regulation.  J Nutr 2000;130(2):272S-275S.
10 Rippe JM, Tappy L.  Sweeteners and health:  findings from recent research and their impact on obesity and related metabolic conditions.  Int J Obes 2016;40:S1-S5.
11 Lowndes J, Sinnett SS, Rippe JM. No Effect of Added Sugar Consumed at Median American Intake Level on Glucose Tolerance or Insulin Resistance. Nutrients 2015;7:8830-8845.

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