Limiting Fructose Intake May Boost Weight Loss
DALLAS – July 24, 2008 – One of the reasons people on low-carbohydratediets may lose weight is that they reduce their intake of fructose, atype of sugar that can be made into body fat quickly, according to a researcher at UT Southwestern Medical Center.
Dr. Elizabeth Parks, associate professor of clinicalnutrition and lead author of a study appearing in a current issue of the Journal of Nutrition, said her team’s findings suggest that the right type of carbohydrates a person eats may be just as important in weight control as the number of calories a person eats.
Current health guidelines suggest that limiting processed
carbohydrates, many of which contain high-fructose corn syrup, may help
prevent weight gain, and the new data on fructose clearly support this
recommendation.
“Our study shows for the first time the surprising speed with which
humans make body fat from fructose,” Dr. Parks said. Fructose, glucose
and sucrose, which is a mixture of fructose and glucose, are all forms
of sugar but are metabolized differently.
“All three can be made into triglycerides, a form of body fat; however,
once you start the process of fat synthesis from fructose, it’s hard to
slow it down,” she said.
In humans, triglycerides are predominantly formed in the liver, which
acts like a traffic cop to coordinate the use of dietary sugars. It is
the liver’s job, when it encounters glucose, to decide whether the body
needs to store the glucose as glycogen, burn it for energy or turn the
glucose into triglycerides. When there’s a lot of glucose to process, it
is put aside to process later.
Fructose, on the other hand, enters this metabolic pathway downstream,
bypassing the traffic cop and flooding the metabolic pathway.
“It’s basically sneaking into the rock concert through the fence,” Dr.
Parks said. “It’s a less-controlled movement of fructose through these
pathways that causes it to contribute to greater triglyceride synthesis.
The bottom line of this study is that fructose very quickly gets made
into fat in the body.”
Though fructose, a monosaccharide, or simple sugar, is naturally found
in high levels in fruit, it is also added to many processed foods.
Fructose is perhaps best known for its presence in the sweetener called
high-fructose corn syrup or HFCS, which is typically 55 percent fructose
and 45 percent glucose, similar to the mix that can be found in fruits.
It has become the preferred sweetener for many food manufacturers
because it is generally cheaper, sweeter and easier to blend into
beverages than table sugar.
For the study, six healthy individuals performed three different tests
in which they had to consume a fruit drink formulation. In one test, the
breakfast drink was 100 percent glucose, similar to the liquid doctors
give patients to test for diabetes – the oral glucose tolerance test. In
the second test, they drank half glucose and half fructose, and in the
third, they drank 25 percent glucose and 75 percent fructose. The tests
were random and blinded, and the subjects ate a regular lunch about four
hours later.
The researchers found that lipogenesis, the process by which sugars are
turned into body fat, increased significantly when as little as half the
glucose was replaced with fructose. Fructose given at breakfast also
changed the way the body handled the food eaten at lunch. After fructose
consumption, the liver increased the storage of lunch fats that might
have been used for other purposes.
“The message from this study is powerful because body fat synthesis was
measured immediately after the sweet drinks were consumed,” Dr. Parks
said. “The carbohydrates came into the body as sugars, the liver took
the molecules apart like tinker toys, and put them back together to
build fats. All this happened within four hours after the fructose
drink. As a result, when the next meal was eaten, the lunch fat was more
likely to be stored than burned.
“This is an underestimate of the effect of fructose because these
individuals consumed the drinks while fasting and because the subjects
were healthy, lean and could presumably process the fructose pretty
quickly. Fat synthesis from sugars may be worse in people who are
overweight or obese because this process may be already revved up.”
Dr. Parks said that people trying to lose weight shouldn’t eliminate
fruit from their diets but that limiting processed foods containing the
sugar may help.
“There are lots of people out there who want to demonize fructose as the
cause of the obesity epidemic,” she said. “I think it may be a
contributor, but it’s not the only problem. Americans are eating too
many calories for their activity level. We’re overeating fat, we’re
overeating protein; and we’re overeating all sugars.”
Some data were collected at the University of Minnesota, where Dr. Parks
worked before joining the UT Southwestern faculty in 2006.
Comments
2 Responses to “Limiting Fructose Intake May Boost Weight Loss”
Feel free to leave a comment...
and oh, if you want a pic to show with your comment, go get a gravatar!
I need to lose about 35 pounds and I’ve had friends that have good success with low carb diets, but I have high cholesterol so that isn’t an option for me. What kind of diet would you suggest for me to lose weight? Thanks – Julie
Hi Julie,
Thank you for your question. First off, there is no one right diet that would work for even half of the population. Each of us has our own unique biochemistry, so what worked for your friend may not work for you. Therefore diet plans should be customized to meet your individual needs.
With that said, the low-carb diets certainly do help people lose weight. Research studies over the past several years have revealed surprising results from the Atkins or South Beach type of diets that are low in carbs and higher in fat and/or protein. In the case of such diets, it seems that the protein and fat help curb hunger so that you eat fewer calories overall, thereby leading to weight loss. People are much more satiated on these diets vs. low fat diets, so they are also more sustainable. Surprisingly, many people see an improvement in their cholesterol and triglyceride numbers on the low carb diets, even when eating high-fat and high-protein amounts as with Atkins. So even though you have high cholesterol, something like the Atkins diet can work in the short term.
One of the reasons these diets are so popular is that they are so radical, requiring drastic changes to the way you eat, which is why people who like to go ‘cold-turkey’ do well with these. However, even with all of the positive research that exists, I’m not a fan of low carb diets for long-term use. The longest research study spanned 1 year, so there are questions as to its effect on bones, kidneys and intestinal health as time goes on.
For the long term, I recommend a diet with a more balanced approach. The American Journal of Clinical Nutrition recently published a research a paper which studied a ‘high-protein’ diet made up of 30% of calories from protein and about 50% of calories coming from carbohydrates. Participants in the study reported greater satisfaction, less hunger, and weight loss and ate some 441 fewer calories a day when following this variety of high-protein diet. This approach is close to the Mediterranean diet as well as the ‘Zone’ diet, and the lesson to take from these is to make sure you have balanced meals with protein at each meal.
But don’t forget about the power of making simple changes such as getting rid of all processed food. Processed foods are typically those high-carbohydrate foods that can increase weight gain. If you see the words ‘hydrogenated’ or ‘high-fructose corn syrup’ on any food labels, don’t use them. The former has been linked to vascular disease, and high amounts of fructose are clearly implicated in obesity and causing fatty liver.
Move towards a whole foods diet by eating whole grains, vegetables, nuts, seeds, fish, poultry, lean meats, and some fruit. Trade in diet soda for green tea. Make sure you have adequate protein at each meal, which can help balance blood sugar levels and prevent roller coaster sugar cravings. Eating a nourishing breakfast has been shown to reduce cravings during the day and assist with weight loss.
Here are some additional key points that go for anyone trying to lose weight:
1) Have an exercise routine. It doesn’t have to be an hour or even 45 minutes at the gym: just take brisk walks at least every other day. Our bodies are designed for physical activity, and regular exercise is imperative to lose weight and to keep it off.
2) Eat your vegetables. They’re low in sugars and offer a plethora of beneficial phytochemicals for good health. Focus on cabbages, onions, garlic, broccoli, carrots, and celery.
3) Eat whole foods. Whole grains such as rice, millet, quinoa. Raw almonds, walnuts, cashews. Fresh vegetables and fruits. Fish, lean poultry and meats.
4) Minimize nighttime desserts. Those late night sugary foods are easily converted to adipose tissue, i.e. fat. (If necessary, you can take a brisk walk after dessert to help burn those simple sugars.)
5) Don’t feel deprived. This one may be hard when not having dessert at night, but it is important to substitute healthy choices for unhealthy ones. If you really need some chocolate, get some 80% organic dark chocolate.
6) Be patient. Research shows that quick weight loss most often leads to quick weight gain down the road. The slower you lose, the longer you lose.
In Health,
George Mandler
Licensed Acupuncturist
Licensed Dietitian / Nutritionist
Maynard, MA & Cambridge, MA