T Nation

Fattening Fructose Article

Don’t know if anybody posted this yet:

And if you’re pressed for time, the pith:

In the study, researchers compared the effects of feeding mice fructose-sweetened water, a soft drink sweetened with sucrose (table sugar), a diet soft drink, or water. The mice were allowed to drink as much as they wanted of their designated beverage.

The mice that drank the fructose-sweetened water gained significantly more body fat than the others, even though they decreased the amount of calories they ate from solid food.

“We were surprised to see that mice actually ate less when exposed to fructose-sweetened beverages, and therefore didn’t consume more overall calories,” says Tsch?p. “Nevertheless, they gained significantly more body fat within a few weeks.”

If this carries over to humans, it looks like another sizeable nail in the coffin of the “a calorie is a calorie” crowd.

I noticed in the article that the group of mice who drank the “diet” soft drink gained a couple more BF% points’s than the ones who consumed water. Has anybody heard anything else about artificial sweetners being a deceiving source of fat gain?

Who cares? I still gobble down fruits and fruit juice like no other, and I don’t have a problem keeping the weight off. Same goes with caffeine or any carbs past 6pm. I don’t care, Im living my life. i don’t like pop cause it cramps me up and gives me heartburn. So Im gonna drink a dam juicy juice if I wanna. Water gets boring.

People seem so carb fearfull lately, reminds me of the old days when fat was bad.

Everything in balance people. Nutrition isn’t rocket science.

[quote]skaklight wrote:
I noticed in the article that the group of mice who drank the “diet” soft drink gained a couple more BF% points’s than the ones who consumed water. Has anybody heard anything else about artificial sweetners being a deceiving source of fat gain?[/quote]

I still don’t understand why the mice that were fed water with their food also gained weight. Were they overfeeding all these mice to begin with? That wasn’t clear in the article.

But you’ll notice that they don’t mention which of the other groups of mice actually ate more than average, only that the fructose mice ate less.

I know that Lonnie Lowery has talked about the possibility that diet sodas (or any artificial sweeteners) may have a tendency to cause overeating later in the day as compensation for the perceived ingestion of sugar without the actual calories of the sugar. Seemed kinda crazy to me, but then again, the Lonman is a smart dude.

[quote]Velvet Revolver wrote:
Who cares? I still gobble down fruits and fruit juice like no other, and I don’t have a problem keeping the weight off. Same goes with caffeine or any carbs past 6pm. I don’t care, Im living my life. i don’t like pop cause it cramps me up and gives me heartburn. So Im gonna drink a dam juicy juice if I wanna. Water gets boring.

People seem so carb fearfull lately, reminds me of the old days when fat was bad.

Everything in balance people. Nutrition isn’t rocket science.
[/quote]

I agree; I would never stop eating a food or change my diet drastically based on the results of one test. That would be foolish; especially when it comes to healthy food like fruit. Of course, if this persuades you to give up that sugary granola bar that you might otherwise have eaten, I think that’s probably a good thing.

Anyway, moderation is definitely key, but it can also be a tricky animal. Case in point: I personally try to get about 0.75g to 1g of protein / lb lean bodyweight per day in an effort to be moderate. But plenty of people on this site would call me a fool for eating so little, while the average person calls me a health nut and thinks I’ll be dead of kidney disease in five years. It’s all relative.

I don’t know exactly what implications this has for humans. I eat high-fiber, low GI fruit all the time, even when leaning out. With no problems. And I’m not that naturally lean. The container also matters very much. Sure it’s ‘sugar’, but table sugar and sugar from fiber-rich fruit is very different. Interesting article though.

[quote]skaklight wrote:
I noticed in the article that the group of mice who drank the “diet” soft drink gained a couple more BF% points’s than the ones who consumed water. Has anybody heard anything else about artificial sweetners being a deceiving source of fat gain?[/quote]

Yes; there was something I think on this site a bit ago about that. When you consume a lot of artificial sweetener your body down-regulates the feeling of satiation caused by consuming something sweet. So when you eat stuff that’s naturally sweet it causes you to feel less satiated b/c your body believes it has less calories than it actually does.

I ran across the info below a couple of years ago.

Does Fruit Make You Fat?

By Patrick Gamboa B.S.

The old adage that your body is a temple is well known and still has relevance today. Without a solid foundation a temple can not be successfully constructed and will eventually collapse. The same holds true for the human body. We at ISSA strive to educate our trainers regarding the synergism between proper exercise, nutrition and behavior modification to effectively draw their clientele into not just a good lifestyle, or even a better lifestyle, but the best way of life; a fitness lifestyle.

The importance of nutrition is imperative as the foundation of any successful fitness program. The core of this foundation should be based around food. Just as certain compounds are necessary to build a solid foundation in a building, specific foods are necessary to build a solid nutritional foundation. Since we have already discussed which foods aid in building this foundation through past articles, we will focus our attention on why certain foods that are considered healthy, actually may not aid in fat reduction.

With the advent of so many nutritional approaches to achieve the ideal look, numerous inquiries regarding the practice of omitting fruit, fruit juices or any of its derivatives from a diet have surfaced. Fruit is a healthy food, full of nutrients, high in fiber, vitamins, minerals, and low in fat and calories. It is a common practice for bodybuilders during pre-contest preparation to omit fruit from their diets, as it should be for anyone looking to minimize bodyfat. We will discuss the chemistry behind the efficacy of this practice.

Our bodies can only absorb monosaccharides (glucose, galactose, or fructose), the single units of sugars and starches. Once absorbed through the small intestines into the portal vein, and then circulated into the bloodstream through the liver as blood glucose, our bodies can put glucose to work in three ways:

  1. It can burn the glucose immediately for energy if blood glucose levels are not at a stable level of 20 grams blood borne glucose circulating per hour.
  2. If it is not needed for energy immediately, then it is converted into glycogen in the liver or muscles. The liver has the capacity to store 100 grams of glycogen. The muscles have the capacity to store between 250-400 grams of glycogen, depending on muscle mass and physical condition. Liver glycogen supplies energy for the entire body. Muscle glycogen only supplies energy to muscles.
  3. If the body has an excess of glucose, and all of the glycogen stores are full, the surplus glucose is converted to fat by the liver and stored as adipose tissue (bodyfat) around the body. If needed, fatty acids can be burned as fuel (BUT the fat cannot be converted back to glucose).
    Now that we have outlined how our bodies use glucose, we will discuss why fruit (fructose or fruit sugar) is detrimental in an attempt to maximize fat loss. Since muscles have the specific purpose of contraction, they have a limited number of enzymes for glycogen synthesis. Muscle only has the necessary enzymes to convert glucose (and nothing else) into glycogen. The liver, however, is able to make glycogen from fructose, lactate, glycerol, alanine, and other three-carbon metabolites. Muscle glycogen, which is similar in structure to starch, is an amylopectin (branched chained polymer containing hundreds of glucose units). Unlike muscles, which can only supply energy to themselves through the stored 250-400 grams of glycogen, the liver is responsible for supplying energy to the entire body.

If you have fruit, fruit juice, or any of its derivatives, the following conditions occur:

Referring to the three ways the body uses glucose, assuming that blood glucose levels are adequate, the glucose will then be stored as glycogen. Muscle does not have the necessary enzymes to synthesize fructose into glycogen; therefore the liver converts this fructose into liver glycogen. It would only take three, 8-ounce glasses of orange juice to fully replenish liver glycogen stores. Since the liver is responsible for supplying energy to the entire body, once its stores are full, a rate limiting enzyme in glucose metabolism which is responsible for signaling the body to store glucose as glycogen or convert it to fat (phosphofructokinase), signals the body that all stores are full. If the glycogen stores are signaled as full, then the third way our body uses excess glucose is to convert it to fatty acids and store as adipose tissue. In essence, fruit sugar is easily converted to fat.

Many may be asking why then is fruit low on the glycemic index? If it does not cause a sudden release of insulin, then how could it ever be a poor food choice? Once the fructose (fruit sugar) enters the liver and liver glycogen is already full, then it can not be used by the muscles for glycogen or energy production. It is converted to fat and released back into the bloodstream to be stored as adipose tissue. The low glycemic response is based on the fact that fructose leaves the liver as fat, and fat does not raise insulin levels.

This is the biochemistry behind the recommendations to limit fruit in your diet. As mentioned, fruit is a very nutritious food full of vitamins, minerals, fiber, and low in calories and fat. If your goal is to exclusively to minimize bodyfat, then it is advisable that you consume more complex carbohydrates, which will go to replenishing muscle glycogen stores rather than fruit, which will only replenish liver glycogen stores, and is useless in muscle glycogen replenishment.

References:

  1. Costill DL, Sherman WM, Fink WJ, Witten MW, and Miller JM. The role of dietary carbohydrates in muscle glycogen resynthesis after strenuous running. Am. J. Clin. Nutr. 34: 1831-1836, 1981.
  2. Shafrir E. Fructose/sucrose metabolism, its physiological and pathological implications. Sugars and Sweeteners, Kretchmer N and Hollenbeck CB, Eds. CRC Press, 1991pp. 63-98.
  3. Herbert V, Subak-Sharpe GJ. Total Nutrition: The Only Guide You’ll Ever Need. St Martins Press, 1987 pp. 54-55.

? 1998-2001 ISSA All Rights Reserved

Chris Shugart and I discussed this in our Double Tap (audio) interview at the left of your screen.

There is some research, although mixed, that artificial sweeteners may not help fat loss efforts when used as a crutch.

[quote]skaklight wrote:
I noticed in the article that the group of mice who drank the “diet” soft drink gained a couple more BF% points’s than the ones who consumed water. Has anybody heard anything else about artificial sweetners being a deceiving source of fat gain?[/quote]

I didn’t read the entire posted article but here’s the cliffs notes on fructose:

It bypasses the rate limiting step in glycolysis (the main carb metabolizing pathway) which can lead to a “flood” of end-product (i.e. pyruvate and acetyl Co-A). This, in excess, can be assembled into fat (fatty acids/ triacylglycerols) before it can be “burned”.

I have repeatedly seen data showing serum triglycerides rising significantly after consumption of fructose. It’s a little scary - as if the subjects ate fat rather than sugar.

(And before anyone asks: no, whole fruit is not fattening… although guzzling fruit juices at inopportune times may be.)

[quote]Lonnie Lowery wrote:

(And before anyone asks: no, whole fruit is not fattening… although guzzling fruit juices at inopportune times may be.) [/quote]

Good. That’s what I’ve always thought. Also, how about other macronutrients changing the way the body metabolizes fruit (or carbs in general)? I rarely have fruit alone. Usually with protein. Maybe as a side with a protein-rich salad and a lowfat or nonfat dressing.

I’d like someone to try and tell me that consuming a lot of “High Fructose Corn Syrup,” such as in soda pop won’t make them fat…

[quote]CU AeroStallion wrote:
I’d like someone to try and tell me that consuming a lot of “High Fructose Corn Syrup,” such as in soda pop won’t make them fat…[/quote]

No one would try to tell you that

The sugar in fruit is not 100% fructose either. For example: Apples – about 55% fructose, the other 45% sucrose and glucose. Grapes are about 45% glucose. Cherries are about 55% glucose.

[quote]rmetz wrote:
The sugar in fruit is not 100% fructose either. For example: Apples – about 55% fructose, the other 45% sucrose and glucose. Grapes are about 45% glucose. Cherries are about 55% glucose.[/quote]

I was going to point this out too. Also, complex carbs are made of chains of simple sugars. Therefore they contain fructose as well as glucose, so I don’t see how they are so much better.