Does Fructose Make You Fat?

Janet Bond Brill, PhD, RD, LDN

For a study conducted by Yale University School of Medicine and published in the prestigious medical journal JAMA, twenty healthy adults were given either a fructose or a glucose drink. MRI scans of the participants’ brains were then analyzed for blood flow and brain activity in regions of the brain that regulate appetite. The findings showed that ingestion of glucose, but not fructose, reduced blood flow and brain activity in regions of the brain that regulate appetite, and led to higher levels of hormones that produce feelings of fullness and satiety. In other words, only glucose was able to turn off those areas of the brain that drive you to eat more. Fructose, on the other hand, appears to increase food-seeking behavior and cause you to eat more.

What is fructose?
There are three molecules (simple sugars) that make up all the various kinds of carbohydrates we eat: glucose, galactose, and fructose (aka fruit sugar). In our diet, fructose intake is derived from two sources: as a natural compound in fruit, and as an added ingredient of processed foods.

It is the fructose added to the processed foods we eat that is the real villain. The main source of fructose in processed foods comes in form of the sweetener called high fructose corn syrup, or HFCS. HFCS has a different chemical makeup than table sugar. It generally consists of ~55 percent fructose and can be as high as 90 percent fructose. The other “simple sugar” in HFCS is glucose (a.k.a. blood sugar), generally found in a concentration of about 42 percent.

HFCS comes in the form of sweet, thick syrup and is derived from corn. Table sugar, on the other hand, is half glucose and half fructose, and is derived from sugar cane or beets, and has a granular consistency. HFCS is used primarily in soft drinks (HFCS is the only caloric sweetener in soft drinks), and other sweetened beverages such as lemonade and apple juice, in baked goods, condiments, and many additional types of processed foods. Two thirds of all the HFCS consumed is in the form of sweetened beverages.

HFCS is the preferred sweetener over table sugar because it is inexpensive to make and blends well with food. In the 1980’s, food manufacturers improved methods of producing HFCS, making it cheaper than table sugar. HFCS is made from corn, so it is far less costly than table sugar from sugar cane. Translation: HFCS saves food manufacturers lots of money, in fact, hundreds of millions of dollars in savings.

How much do we eat?
Our consumption of HFCS has skyrocketed over the past several decades, from 0 consumption in 1966 to approximately 63 pounds per person per year (annual per capita intake) in 2001. According to the Center for Science in the Public Interest (CSPI), each person in the United States consumes on average about 69 pounds of corn-based sweeteners such as HFCS every year, translating into approximately 30 teaspoons per day. So, a single 12-ounce can of soda has as much as 13 teaspoons of sugar in the form of HFCS.

This is far greater than the American Heart Association (AHA) recommends as the maximum level of added sugar for heart health. In fact, added sugars have made the AHA blacklist of foods that if eaten in excess contribute to heart disease, which is the leading cause of death in men and women in the U.S. today. AHA’s guidelines for sugar intake call for an upper limit of no more than 100 calories per day in women (about 6 teaspoons of sugar), and 150 calories per day (about 9 teaspoons of sugar) in men.

Does fructose make you fat?
New research suggests that the body metabolizes the fructose in HFCS differently than it does old-fashioned cane or beet sugar, which in turn alters the way metabolic-regulating hormones function.

The end result is that our bodies are essentially tricked into wanting to eat more, which would clearly contribute to weight gain.

The rise in HFCS consumption in the U.S. over the last several decades has mirrored the rise in overweight and obesity, leading some researchers to suggest that HFCS may be a causal factor in the obesity epidemic. Considering that the development of overweight and obesity is related to excessive calorie intake, and that numerous studies have reported an association between soft drink consumption and weight gain, I support the notion that HFCS intake is a contributing factor in the country’s growing obesity problem. Furthermore, soft drinks are the leading source of simple sugar in our teenagers’ diets, suggesting that excessive HFCS intake is also related to the development of childhood obesity.

Not everyone agrees. There is currently a debate about whether HFCS is driving the obesity epidemic. In 2012, an extensive review of the topic was published in the International Journal of Obesity. The takeaway message from the review was that there is not enough evidence that consumption of HFCS is to blame for the obesity crisis.

Dr. Janet’s advice
HFCS is a refined sugar, a concentrated source of calories with no other nutrients, and is therefore considered as “empty calories” by nutritionists. What’s more, consumption of HFCS containing processed foods replaces more nutritious foods, and therefore decreases one’s intake of healthful nutrients such as vitamins and minerals, amino acids, essential fatty acids, and fiber. Soft drinks are considered an “energy-dense” food, providing a great deal of calories in small volume that can be consumed quickly.

There are numerous serious health problems associated with the consumption of excessive quantities of HFCS such as obesity, high triglycerides, and diabetes mellitus, to name a few. In fact, a high HFCS intake (and the associated weight gain) has also been linked with the development of the metabolic syndrome – a dangerous cluster of conditions that occur together, including high blood pressure, abdominal obesity, an abnormal blood lipid profile, and high insulin levels. Metabolic syndrome significantly increases ones risk for heart disease, stroke and diabetes. While HFCS may have roles in some health conditions, the excessive use of any type of sugar may be bad for general health and weight control. Your best bet is to cut your intake of liquid calories from sodas, the main source of appetite-stimulating fructose. If you eat a diet that contains lots of unprocessed, natural foods such as fruits and vegetables, whole grains, nuts, and olive oil, grown the way nature intended and free of unhealthful additives, you automatically cut down on your intake of potentially harmful ingredients such as HFCS, sodium, saturated fat and cholesterol.

Janet Bond Brill, PhD, RD, LDN is author of the books, “Prevent a Second Heart Attack, 8 Foods, 8 Weeks to Reverse Heart Disease” (Random House/Crown Publishing 2011) and “Cholesterol Down: 10 Simple Steps to Lower Your Cholesterol in 4 Weeks Without Prescription Drugs” (Random House/Crown Publishing 2006). She is a leading diet- and nutrition writer, educator and practitioner, and consults for the health- and fitness industry, specializing in cardiovascular disease prevention. For more information, please visit: or

The articles written by guest contributors are the sole responsibility of the individual writers in terms of factual accuracy and opinion and do not necessarily reflect the views of the publisher of this blog.

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