Sport Evils of Fructose

Sport Fitness
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The Evils of Fructose

 by Cassandra Forsythe, PhD(c), CSCS, CISSN​

Are you looking for that nutritional edge to get your body composition to the next level?
Have you been eating your "five-a-day" like a good boy should, but just can't shake that last bit of icing off your jelly belly?

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Well, take close note: if you reduce the fructose in your diet, you will lose that stubborn body fat!

Fructose Metabolism 101, the simplified version
Fructose is a type of simple sugar (a carbohydrate in its simplest form) that is much different than its sister sugar, namely glucose. When you eat fructose, it's absorbed more slowly in the intestine, and its absorption is slightly limited.
Some people—like those with diabetes, see fructose as a superior simple sugar because it doesn't get used as quickly or as efficiently. What they don't realize, is that fructose is normally consumed at the same time as glucose, which speeds up the absorptive process.
Once fructose passes through the intestine, it's quickly taken to the liver for processing. Here, it has two fates: it's either turned into glucose and then stored as liver glycogen; or it's used for energy by liver cells.
Unlike glucose, fructose can only be metabolized in the liver, whereas glucose can be passed to other body tissues, like your muscles.

Why fructose is a problem for dieters:
If you have a lot of fructose in your diet, it only has one place to go: your liver. If your liver glycogen levels are full, which is the case all times of the day except before you eat breakfast, then that fructose is turned into fat!
Since your liver doesn't want to store this new fat, it ships it to other parts of your body; places you don't want it, like your abdomen or lower back.
Do you now see why too much fructose in your diet can be one of the biggest reasons you can't shrink those last few fat cells?

How do I avoid eating fructose?
When people hear the word fructose, they usually think fruit. Ready for a shocker? Fruit is actually not the major source of fructose in your diet!
Yes, it does have fructose, but only certain fruits are high in it, while others are relatively low. Not all fruits are bad for your body composition; vegetables are the same way.

The major contributors of fructose in your diet, in descending order, are as follows:

 • High Fructose Corn Syrup (HFCS)
• Table Sugar, which is a 50:50 combination of glucose and fructose
• Brown Sugar
• Maple Sugar
• Cane Sugar
• Molasses
• Honey
• Concentrated Fruit Juice
• Fruits
• Vegetables

Avoid the top eight in this list at all costs!. Read labels carefully, because HFCS is hiding in almost every food you eat nowadays. And, just because honey is natural, doesn't mean you should use it in abundance.

How do we really know fructose makes your fat?
You must have been living under a rock if you haven't already heard about HFCS being related to every common human disease we face today, such as diabetes, heart disease, obesity and cancer.
This relationship was first discovered in lab experiments with rodents. (1) When a high fructose diet (about 50-60% of total energy intake) is given to rats, they present symptoms of the Metabolic Syndrome, which is the precursor to full-blown diabetes and heart disease.
These animals develop high blood pressure, endothelial dysfunction, weight gain, increased abdominal fat, hyper-triglyceridemia, and insulin resistance. The weight and fat gain is thought to be due to leptin resistance; rats that eat a high fructose diet long-term have higher leptin levels than rats that don't eat a lot of this simple sugar.


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Researchers then concluded that in humans, it's the fructose and not glucose that begins the cascade of Metabolic Syndrome risk markers (2); and this seems to be initiated by insulin resistance. Men forced to eat experimental high fructose diets develop insulin resistance within a week (3), compared to no insulin abnormalities in people given a high starch diet.
Sucrose, also known as "table sugar" (glucose and fructose combination), is even worse: people given a 28% sucrose diet for 10 weeks not only develop insulin resistance, but also gain weight and have increased blood pressure!
In another study, when overweight women were put on a "no-restriction" diet high in either sucrose, fat, or starch, only the high starch diet group lost weight and body fat. (4)
Today, most Americans are eating about 70-100 grams of fructose per day, and we're getting fatter by the minute. In bright contrast to today's world, this nation consumed just 15 to 40 grams of fruit & veggie-derived fructose in the 19th century, when we weren't even close to being this chubby. (5)

Why does fructose cause fat-gain?
Fructose and fructose-containing foods will usually make your meals taste better, so you end up eating much more than necessary. They also fail to make you feel satisfied after you eat them, due to inadequate stimulation of leptin and ghrelin, the two satiety hormones. (6)
There is also evidence that fructose slows your metabolism: kids who drink sodas and fruit juices (both are rich in HFCS and fructose) are fatter than those who don't drink them, but who eat the same amount of calories. (7)

So, what kinds of fruits and vegetables can I eat and not get fat?
Although fruit does contain some fructose, it's not the only sugar that it contains. Fruit is beneficial for you because it's the best natural source of antioxidants that help you fight free-radicals, a major cause of aging and muscle damage. It's also an important source of fiber.
Your best bet is to choose fruits that are low in fructose, and only eat the higher fructose fruits in the morning, when your liver glycogen levels are low. At this time, your liver can use or store the fructose without converting it to fat.

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The following fruits are highest in fructose (per typical serving size)*. They contain more than 4 grams of fructose per serving.

Stay away from these outside of an occasional breakfast:

 • apple
• banana
• cherries (1 Cup)
• grapes (1 Cup)
• mango
• melon (2 wedges)
• orange
• pear
• pineapple (2 rings)
• watermelon (1 large slice)

These fruits are lowest in fructose; they contain less than 4 grams of fructose per serving.

You can eat these with less restriction:

 • apricot
• avocado (1/3 medium; yes, it's a fruit)
• blackberries (1/2 cup)
• figs
• grapefruit (1/2 medium)
• papaya
• peach
• plum
• raspberries (1/2 cup)
• strawberries (1/2 cup)
• tomato (yes, also a fruit)

*Note, these values were calculated by adding all of the fructose plus half of the sucrose per typical serving size (i.e., a typical apple weighs 120 grams).

Vegetables are much lower in fructose than fruits. The highest fructose-containing vegetables are corn and sweet potatoes, and they only have roughly 1.2 grams of fructose per serving. If you're really trying to keep this sugar low, also avoid white potatoes and green peas.

Bottom Line:
Fructose may be one of the reasons your body is not dropping the stubborn body fat you've been fighting for weeks, or even months. Before you start avoiding the produce section of the grocery store, start scanning the labels of some of your most frequently consumed foods.
Does your salad dressing contain HFCS? Do you douse your morning eggs with HFCS-laden ketchup? Or maybe you're known to eat "all-natural" products made with honey?
Once you've eliminated these major fructose-suspects, turn to your fruit intake. Don't eliminate it completely because some fruit will aid your overall health and studliness by fighting free-radical-induced aging and muscle damage. Just choose fruits lower in fructose.
Apples may keep the doctor away, but with their high fructose content, they'll keep your six-pack just as out of sight.


About the author:
Cassandra Forsythe is a Ph.D. candidate at the University of Connecticut studying exercise science and nutrition. She received her M.S. in Human Nutrition and Metabolism and her B.S. in Nutrition and Food Science from the University of Alberta in Edmonton, Canada. She is certified as a Strength and Conditioning Specialist (CSCS) from the National Strength and Conditioning Association (NSCA), and is a Certified Sports Nutritionist (CISSN) through the International Society of Sports Nutrition ().

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At UConn, Cassandra studies under Jeff Volek, PhD, RD researching the effects of low-carbohydrate ketogenic diets and resistance exercise on risk factors for heart disease, diabetes and body composition. She works as a nutritional educator and weight-loss coach and is the author of two popular books for women: "The New Rules of Lifting for Women", co-authored with Lou Schuler and Alwyn Cosgrove, and "Women's Health Perfect Body Diet". In August 2008, she will begin her dietetic internship to become a Registered Dietitian and will complete her PhD in January 2009. She can be reached at her .

References
1. Segal MS, Gollub E, Johnson RJ (2007) Is the fructose index more relevant with regards to cardiovascular disease than the glycemic index? Eur J Nutr 46:406-417
2. Elliott SS, Keim NL, Stern JS, Teff K, Havel PJ (2002) Fructose, weight gain, and the insulin resistance syndrome. Am J Clin Nutr 76:911–922
3. Beck-Nielsen H, Pedersen O, Lindskov HO (1980) Impaired cellular insulin binding and insulin sensitivity induced by high-fructose feeding in normal subjects. Am J Clin Nutr 33:273–278
4. Raben A, Vasilaras TH, Moller AC, Astrup A (2002) Sucrose compared with artificial sweeteners: different effects on ad libitum food intake and body weight after 10 wk of supplementation in overweight subjects. Am J Clin Nutr 76:721–729
5. Raben A, Macdonald I, Astrup A (1997) Replacement of dietary fat by sucrose or starch: effects on 14 d ad libitum energy intake, energy expenditure and body weight in formerly obese and never-obese subjects. Int J Obes Relat Metab Disord 21:846–859
6. Teff KL, Elliott SS, Tschop M, Kieffer TJ, Rader D, Heiman M, Townsend RR, Keim NL, D'Alessio D, Havel PJ (2004) Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women. J Clin Endocrinol Metab 89:2963–2972
7. Dennison BA, Rockwell HL, Baker SL (1997) Excess fruit juice consumption by preschool-aged children is associated with short stature and obesity. Pediatrics 99:15–22
 
The Forbidden Fruit?
by Cy Willson


In the beginning, God created the heaven and the earth. Later, He formed man of the dust off the ground and breathed into his nostrils the breath of life. He told Adam to lift heavy rocks and logs and turn his body into a temple. He saw that this was good. With Adam in shape, He also saw that it could lower His employee insurance rates. Also good.

One day, Adam noticed that there were no chicks in the garden, so God whipped him up one and called her Eve, which literally means "first babe" in Hebrew. Eve was cool, but one afternoon while Adam was watching "Battledome," she brought him a piece of fruit from the tree of knowledge and used her womanly ways to convince him to eat it. Suddenly, a voice boomed from the heavens, and God said:

"Don't you know that fruit is just nature's sugar? If you eat it, you'll get fat from all of the fructose!"

Since God would not have any chubsters in his paradise, he booted Adam and Eve out of the Garden of Eden. In fact, fruit is so bad for you that some time later, God wrecked the entire town of Sodom after hearing about all of the "fruits" who lived there.

See? Fruit is evil. Even the Bible says so! At least, that's what the anti-fruit brigade would have you believe. Well, I'm here to play the serpent and tell you that bodybuilders and athletes should make fruit a regular part of their diets. Not only will it not make you fat, you'll probably see better progress in your muscular gains and overall health by chomping down on an apple or banana a day!


Revelation: Fruit Isn't So Bad After All

Let's take a look at why fruits have been unjustly bashed by many fitness experts. Basically, it all comes down to fructose. Fructose is the main type of sugar found in fruits, but it's utilized differently by the body than other sugars.

Normally, when a sugar — especially a monosachharide — is ingested, blood glucose begins to rise (glucose can also enter cells without insulin, such as after exercise, but that's another story). The body then senses that blood glucose levels are too high and, since it can't simply expel the glucose, it stores it in muscle and liver tissue for later use. This brings the blood glucose back down — too low, actually — which accounts for the "bonk" (feeling of lethargy) that you get after a so-called sugar rush.

Glucose gets inside of muscle by using a special key. That key is insulin. Insulin binds to receptor sites and allows glucose to pass into the muscle cells. This sounds like a good deal, but here's the catch: insulin also acts as a key to store glucose in fat cells. Hence, the low-carb diet craze, the popularity of the glycemic index, and the oft-irrational fear of fruit and fructose.

Based on the facts above, these nutrition experts often label all sugars, including fructose, as "bad." In effect, they're throwing out the baby with the bathwater. Here's why. Fructose is an insulin-independent monosachharide. This means that it converts into glucose and is stored without the action of insulin (or, at least, insignificant amounts). Fructose doesn't cause a large rise in blood sugar and, consequently, won't raise insulin levels. In short, you won't crash, and energy levels should remain on an even keel.(1)

So, from where does this "fructose gets you fat" myth derive? It's likely that the "experts" took the research on rats too seriously. If you feed Mickey Mouse a large fraction of his bodyweight in sugar, any sugar, then of course he'll become insulin-resistant and his bodyfat will increase. In fact, every study that I've seen showing negative results used astronomical amounts of fructose. Even then, the effects weren't as bad when compared to the overconsumption of glucose.(1)

For you to experience any negative effects from fructose, you'd have to consume around 50-75 grams in a sitting. That's equivalent to eating five to seven apples, one after another. You'd have to eat three or four of these "servings" a day, for a grand total of 15-28 pieces of fruit! As they teach us to say in college...well, duh! If you eat too much of a sugar — or anything, for that matter — you'll get fat.

In fact, fructose has been shown to facilitate both mobilization of endogenous lipid stores and lipid oxidation. For those of you who don't have a medical thesaurus handy, this means that getting a little fructose in your diet might actually help you lose fat.(2) It's even been noted that fructose causes a superior thermic response when compared to glucose or sucrose. The thermic response caused by glucose diminishes with age, but that's not the case with fructose.(3)

Of course, I should mention that fructose has been shown to be lipogenic in a few studies. But, in almost every case, the patients were bedridden in a hospital, suffering from a variety of metabolic disorders. Suffice it to say, bodybuilders seeking to pack on a little more muscle are different from hospital patients.

What about increasing blood triglycerides? Again, those results only appear after large (and rather insane) doses of fructose are administered. Even then, xylitol (a sugar alcohol used in some MRPs) was shown to increase triglycerides more than fructose.(4)

Another faulty argument used by the anti-fructose crowd is that when you ingest fructose, your body magically stops burning fat and switches to glycogen as fuel, thus preserving fat stores and turning you into a chunky monkey. If this were true, then it would be easy to find studies showing decreased lipolysis and exhausted glycogen stores. Guess what? There aren't any.

In studies using male athletes, both at rest and during exercise, the exact opposite has always been shown. Glycogen stores were always preserved when compared to other sugars or placebos, which means that fat was being burned at a greater percentage.(2,5) Fructose maintains blood glucose and increases fat utilization.(6)

Out of all of the sugars, fructose is the least likely to increase bodyfat. In simple terms, throwing in a few pieces of fruit a day or using an MRP sweetened with a little fructose (like Grow!) won't make you fat, especially when combined with some healthful dietary fats and protein. Sure, most people will still need to keep an eye on daily caloric intake. But as long as you're not taking in more calories than you're using, there's no need to be anal about it and certainly no reason to worry about fructose.

On a side note, Biotest uses fructose (along with sucralose) as a sweetener in Grow! instead of the "iffy" aspartame or the usual maltodextrin filler, which has a much higher glycemic index. Fructose has a GI of only about 31.


Let There Be Light!

Hopefully, I've convinced you that fruit and fructose aren't the sole cause of the downfall of Western society. (Everyone knows that the real culprit is the purple Telletubby with the purse, right?)

In fact, I'd go so far as to say that they're beneficial to your bodybuilding efforts. For example, there's research supporting fructose's protein-sparing effects. The study showed that fructose spared protein while keeping blood sugar levels about the same.(7) It was hypothesized that this occurred because of increased protein synthesis.(8)

Need another reason to throw a few strawberries into your favorite MRP? Well, fructose was also shown to increase the absorption of a few important minerals, like zinc and magnesium — yep, the same two minerals that make up ZMA and support natural testosterone levels. Plus, fructose is sweeter than most other sugars without all of the previously mentioned drawbacks. In fact, it's even become the preferred sweetener of many diabetics.

Adding some fruit to your diet will also provide you with vitamins, minerals, phytochemicals, certain flavones, and fructooligosaccharides. Phytochemicals and flavones can provide astounding anti-carcinogenic properties, as well as lowering some blood fats.(11) Oh, yeah, when compared to all of the tuna fish, egg whites, and oatmeal that bodybuilders eat, just plain fruit tastes good! Even on low-carb plans like the T-Dawg or Anabolic diets, you can still have an occasional piece of fruit. Remember, a cup of strawberries or a medium-sized peach each have only about ten grams of carbs.

Fructooligosaccharides — a true five-dollar word, if there ever was such a thing — also provide some interesting benefits. Fructooligosaccharide is a soluble fiber that's 0.4-0.6 times as sweet as sugar, yet it can't be digested.(12) It can even increase the bioavailability of certain minerals, unlike the "bad" mineral-binding phytates.(13) They've also been shown to have an anti-lipogenic effect. In English, this means that they decrease fat production, probably by lowering glucose and insulin levels.(14,15,16)

Anything else? Yep, fructooligosaccharides can increase the amount of endogenous bifidobacteria in your colon. Bifido are the "good" bacteria that have been shown to increase nitrogen utilization and decrease excretion of certain amino acids.(16,17)

Although all fruits have a relatively low glycemic effect, some vary rather significantly in their GI, probably because of the fructose:glucose ratio and the amount of fiber contained within the fruit. Below are just a few fruits that can be consumed and what times are best to consume them:

Early in the day
• Apples
• Strawberries
• Oranges
• Grapefruits
• Cherries
• Pears

Later in the day (after 6pm) and possibly post-workout
• Grapes
• Bananas*
• Peaches
• Pineapple
• Dates
• Figs*

*Because of higher tryptophan levels, these may be helpful in inducing sleep.

The fruits consumed earlier in the day generally have a low GI (below 50) as to keep blood glucose at a more even level. The fruits labeled for use after 6pm, or after a workout, generally have a higher GI (around 70 or more) in order to rapidly restore glycogen levels and induce a state of sleepiness. This is especially true in the case of bananas and figs.

You might even try consuming five different fruits per day. This will give you all of the health protection that you need, and you'll still keep your carbs low, as long as you don't go hog wild on the dumplings.

Will an apple a day keep the doctor away? Well, maybe. But hopefully, I've convinced you that fruit and the fructose that it contains aren't quite as evil as some make them out to be. So, the next time your "Eve" offers you an apple, take it, and eat up!


References

1) Blakk EE, Saris WH. "Postprandial thermogenesis and substrate utilization after ingestion of different dietary carbohydrates. Metabolism 1996 Oct; 45 (10):1235-42

2) Adolph M, Eckart A. Anaesthesist 1995 Nov; 44 (11): 770-81

3) Fukagawa NK, et al. Metabolism 1995 May; 44 (5): 630-8

4) Otto C. "Influence of fiber, xylitol, fructose in enteral formula on glucose and lipid metabolism in normal subjects" Clinical Invest. 1993 Apr; 71 (4): 290-3

5) Jundrain BJ. "Fructose utilization during exercise in men" Journal of Applied Physiology 1993 May; 74 (5): 22146-54

6) Massicotte D, et al. Journal of Applied Physiology 1986 Sep; 62 (3): 1180-4

7) Gelfand RA. "Protein sparing with intravenous fructose" Metabolism 1986 Jan; 35 (1): 37-44

8) Radrizani D. Surg. Gynecol. Obstet. 1986 Jul; 163 (1): 37-41

9) "Fructose and Mineral Metabolism." American Journal of Clinical Nutrition 1993 Nov; 58 (5 suppl) 771 S-7785

10) Brink EJ, Beynen AC. "Nutrition and Magnesium Absorption." Prog. Food Nutrition Science 1992; 16 (2): 125-62

11) Hollman PC, Katen MB. Chem. Toxicology 1999 Sept-Oct: 37(9-10): 937-42

12) Niness KR. "Inulin and Oligofructose: What are they?" Journal of Nutrition 1999 Jul; 129(7 suppl): 1402s-6s

13) Greger JL. "Mineral Bioavailability." Journal of Nutrition 1999 Jul; 129 (7suppl):14 345-55

14) Delzenne NM, Kok NN. " Biochemical basis of oligofructose induced hypolipidemia in animal models." Journal of Nutrition 1999 J; 129 (7 suppl): 1467 S- 705

15) Grizard, Barthomenf C. "Non-digestible oligosachharides used as prebiotic agents." Reprod. Nutrition Dev. 1999 Sep.-Dec; 39 (5-6): 563-88

16) Roberfroid MB. "Health Benefits of non-digestible oligosachharides." Adv. Exp. Med. Biol. 1997; 427:211-9

17) Roberfroid MB. "Dietary Fiber, Inulin, Oligofructose: A review comparing their physiological effects." Crit. Rev. Food Sci. Nutr. 1993; 33 (2): 103-48
 
I wonder if they're referring to strictly consuming fructose with no other saccharides, it'd then make sense.
 
Why would you want to have high GI fruits at night, wouldn't that spike your insulin and isn't that the worst thing that could happen before you sleep?

I had Peaches last night. So i hope you can prove me wrong :D
 
if the fruit is mostly fructose it won't spike insulin. as fructose goes to the liver.

In the article it says that if your liver stores are full the fructose will just be made into fat.. what if there are tasks around in the body that needs fuling by sugar, wouldn't that make it so the fructose gets converted into glycoses and then sent to work.
Also, if your glycogen stores elsewhere are full and you eat normal insulin spiking sugar, wouldn't the same thing happen? Isn't the quest what sugar is best to eat? Obviously, if you don't need it, it will be converted into fat, but the article makes it seem as if this only happens with fructoses...
 
Phate89 said:
Anyone know the answer to my question?
Click to expand...

One answer is. If a healthy person has already been running very low carbs or no carbs for several days, and the liver stores are low already (and the person is also in a good state of insulin sensitivity) , then eating a night (just before bed) isnt going to have any impact (negatively) and will get stored in the liver for later use. This is one reason eating fruit (like pineapple) isnt going to have any bad effects at night. The person (could have) several grams (and like wise several calories) of fructose absorption left to use up before spill over starts, and even then it gets even more difficult in the face of total calorie deficit in a healthy person that isnt sensitive to carb and/or other forms of sugar.

For example, I ate fruit at night all the time before bed, and lost weight just fine (the bulk of the weight). It didnt matter when I ate, as long as a calorie deficit was present, I lost tissue very easily when body fat was high. I understand this may not represent all people (say a diabetic or other persons very senstive to carbs), but fruit (like fats used to) get an undeserved bad name.


Best regards,


Chillen
 
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Fructose from fruit is fine. It is the tremendous amounts of fructose found in many processed products like bars that are the bad boys. Sure it may be stored as fat, but more importantly is that it disrupts your hunger/satiety hormones; causing you to eat more, which is a lot more significant than a few calories stored as fat.
 
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