This was a question someone asked me on twitter – they had read that fruit sugar is stored as fat, was this true? Fruit sugar is mainly fructose. So I asked a Nutritionist, and they said yes possibly, did I want to try a no fruit diet experiment? Jeeeeez not ANOTHER diet!!??
As always, I needed to see what the experts were saying.
A crude search will provide you with this explanation:
‘One thing you may fail to realize is that fruit contains a lot sugar. Even though it's natural sugar it can still cause weight gain if you eat too much and do not burn it off.’http://www.flat-stomach-exercises.com/forgotten-weight-loss-tips.html
And more scholarly articles that in places refer specifically to science and research:
Fructose is transported into cells via a different transporter than glucose
Once fructose is in the liver, it can provide glycerol, the backbone of fat, and increase fat
Our liver is the major site of fructose metabolism. In the liver, fructose can be converted to glucose derivatives and stored as liver glycogen. The liver can only use and store so much fructose as glycogen at one time. The remainder will be stored as fat; thus, a very high single-serving dose of fructose is much more likely to find a home around your middle (http://bodybasicsbootcamps.homestead.com/bonuses/Fructose_vs_Glucose.pdf)
Glucose can be processed by all cells in the body, by fructose can’t. It bypasses an important step due to its molecular structure, and therefore goes straight to the liver, and is more likely to be stored as fat (http://www.parrillo.com/articles/52.pdf )
But, there is some contradiction:
Relax. Experts have concluded: “The intake of naturally occurring fructose from an unprocessed, whole food diet is low and unlikely to contribute to any negative metabolic consequences.”
Further reading:
Although I am still not completely convinced, there is some suggestion that fructose could be more likely to store as fat. BUT, is that just if you eat TONS of fruit? Who knows?!? So there’s only one way to find out! So I tried it for 2 weeks. Here’s what happened.
What did I do?
· 2 weeks, no fruit (at all!) including no fruit drinks, nothing fruit flavoured, I checked everything I ate for fructose content.
· I replaced fruit with rice cakes, small quantities of nuts, or ham or something similar.
· I drank water instead of fruit drinks.
· I have used no sports drinks or anything of that nature during week 1, and only once during week 2.
· I have still followed the 3-2-1- rules with regards to meal balance (breakfast main meal, medium lunch, light tea, all training before breakfast) read about the 3-2-1 diet here http://melanieryding.blogspot.com/2010/12/what-is-3-2-1-diet.html
· I still drank black coffee.
How was it eating like this?
I found this type of diet exceptionally hard, harder than I thought. I really missed and craved sweet things. I found myself rationalising the fact that I could eat biscuits, for example, because they had no fructose! In cafes, where I would normally choose a banana or an apple for example, I would be very tempted to choose a less healthy option because I craved the sweet taste. Savoury snacks just simply don’t cut it in my opinion!! In fact, now, where I would normally crave fruit, I am now finding my cravings have switched to cakes and biscuits. When I first gave up chocolate, it took 2 weeks to ‘get it out of my system’. All that seems to have happened in this case is somehow I have rationalised the fact that it’s ok to eat biscuits and cakes, because they are not fruit and its fruit I am not allowed!! Of course, this is a ridiculous train of thought! Clearly, there is a real risk here to my wellbeing, health, and training fuel mix!
At times, I also found that exercise was harder, and to be honest felt a lot more lethargic during morning pre breakfast sessions. Some people say it was psychological, I honestly don’t think it was because it didn’t change at all throughout the past 2 weeks. I drank water instead of the usual energy drink, used red bull (which I hated, because it’s fizzy!) but found myself more fatigued, and more muscle aches when usually I wouldn’t have this problem.
It is also worth noting this, the most important thing. During the past two weeks I have been ill, or one kind or another. First I got an eye infection, and then no sooner was I done with that, I got an ear infection. Now it needs to be noted that I am usually a very healthy person, and very rarely visit the doctor. I honestly cannot remember the last time (if ever) that I had an ear infection. It certainly seems a very large coincidence that the main food group that delivers vitamin C is omitted, and I become ill. I would definitely attribute this to eating less fruit.
I quite honestly am relieved to be ‘back to normal’ so to speak!
RESULTS after 2 weeks on a no fruit diet:
Weight difference: -2.5lbs
BMI difference: -0.1
Body fat % difference: no change
Water content difference: no change
What does this mean? My thoughts so far;
Hubby’s first reaction was that maybe because the conversion happens in my liver, the liver is skinnier, but that is all! Who knows!
Personally, I think big changes would be seen more in people who previously had a high fructose diet, (e.g. corn syrup, etc) or an unbalanced diet that contained TONS of fruit. When I look back, a lot of research on this topic is USA based, and I read that they use a lot of high fructose corn syrup. There is clearly research to support this, but the research I have read tends to be on people with a much higher body fat % in the first place.
Further research:
After someone sending me some more research that was another challenge to this theory, I wondered why is fructose was so bad, did energy drinks contain it.
This article is an interesting read, and says that fat is a poor fuel that makes you go slower, but also talks about fat burning and weigh management, embracing the train before breakfast idea that I already do http://www.lakeland100.com/downloads/article3.pdf. He says that training in this way will not yield results but is a weight management tool.
This one, however, talks about fuel for performance, and suggests that despite fruit sugar being bad, a glucose/fructose combination is actually good for you with regards to sports performance: http://www.lakeland100.com/downloads/article4.pdf
Here’s more on this topic:
‘Jeukendrup and his colleagues believe that the glucose-fructose combination works better than glucose alone because having multiple carbohydrate sources allows more carbohydrate to be absorbed from the digestive tract. Research indicates that glucose and fructose have their own separate transport systems in the digestive tract. These transporters help carry ingested glucose and fructose from the digestive tract into cells. However, the glucose transporter can only carry glucose, and once it’s filled, it can’t carry any more. But the revelation is that fructose has its own separate transportation system. So even though the glucose transporter is filled to capacity, the fructose transporter can deliver even more fuel to working muscles. Thus, by providing both glucose and fructose, and taking advantage of both transportation systems, you too can deliver more fuel to your muscles and extend endurance even further.’ http://www.powerbar.com/articles/18/latest-research-on-carbohydrate-recommendations-during-exercise.aspx
I tried to understand why the research suggests that fructose may be more likely to convert to fat, yet I had seen no change. Victoria Haigh (@fitvic on twitter) a nutritional advisor, reminded me that it may take up to 12 weeks to see a change, much like when you first start exercising? I guess she may have a point.
It is also worth noting that everybody is different, therefore the results will not be the same on everyone that tries this. You can see that by the comment Kris made on the first blog on this topic:
‘I actually was looking into this several months back - because I was doing all this good stuff and not "seeing" any changes. Then I started looking into the glycemic index. As a result, I actually did no fruit & no starches for 3 weeks - it was tricky, but I based my meals/snacks around protein and low GI veggies. And I totally noticed a difference. Now I eat fruit and starches (but they aren't the centre of my meals) - but the fruits I eat are typically apples, pears, berries & melons.’
However, there is no getting away from the fact that it actually made NO difference at all to me, and in fact I believe contributed to a weaker immune system.
Many people have said that surely the benefits of fruit outweigh everything else? I tend to agree. I was sent this article, which, although the research is in very early stages, is suggesting that polyphenols and flavanoids (found particularly in fruit) are key to rebuilding muscle. Is this why I ache so much more than normal?
‘In a 2006 edition of the prestigious science journal Cell, Lagouge and colleagues published a study whereby mice underwent a 15-week diet and exercise programme where they were either supplemented with resveratrol or a placebo. After the supplementation period, the results were striking. The mice which had been supplemented with resveratrol had a 33 percent higher peak oxygen uptake, and a near 50 percent greater run time to exhaustion.’
When the researchers took samples of the mice muscle and attempted to look further into the mechanisms behind these increases there was a 2.5 times greater area of mitochondria in the muscle.’ http://www.bikeradar.com/fitness/article/nutrition-can-fruit-make-you-fitter-28854
I certainly think that without fruit and vegetables, I would eat a much less healthy diet. When I searched ‘does fruit make you fitter’ on the internet, I got an article that writes exactly that! Here, they say fruit and vegetables stave off other cravings. http://www.peertrainer.com/diet/why_fruits_and_vegetables_help_you_lose_weight.aspx
When you ask Google can fruit juice make you fat, the answer you will get is yes, because of the amount of sugar that is added to it during production!
I found someone else who tried this experiment too. This will show that different people will get different results: http://www.fitbuff.com/does-fruit-make-you-fat-the-truth-revealed-workout-recap-september-28-october-5-2008/
It’s interesting to note that when he decreased calories, he gained weight. I have in the past been told that in fact, the body goes into starvation mode if you don’t eat enough, and therefore you are more likely to store fuel as fat. It is also worth noting that his workload increased by around 15-20 minutes a day. David Sutton, my strength and conditioning coach (@PerformTrain on twitter) would, I imagine, say that is all you need of strength training to make a difference, regardless of diet.
There is no getting away from it, people are still saying excessive fructose consumption is bad for you.
Fructose, especially its excessive consumption, may increase:
- the risk of abnormal blood clotting ailments and hypertension (high blood pressure)
- the risk of type 2 diabetes
- total blood cholesterol levels (it serves in part as the raw material for the synthesis of cholesterol within the body)
- LDL-“bad” cholesterol levels, and
- blood triglyceride levels, especially in diabetics (fructose has a greater propensity to increase serum triglycerides than glucose).
Excessive consumption of fructose may also cause:
- fatigue, especially in persons who are fructose intolerant
- insulin resistance, and
- obesity.
It is estimated that up to 33 percent of persons are unable to completely absorb fructose due to fructose intolerance (also known as dietary fructose intolerance (DFI) which may cause
- flatulence
- intestinal cramps (abdominal pain)
- bloating, and
- altered bowel habits (diarrhoea) http://www.reducetriglycerides.com/reader_triglycerides_low_fructose_fruit.htm
I do not, however, believe that I excessively consume fructose.
What now for me?
I’m told that eating fructose based foods with protein Slows down conversion to glucose & regulates release of insulin. Insulin is needed to properly utilize the energy stored in carbohydrate. This process can be better explained here: http://www.shapefit.com/diet/sports-nutrition-during-exercise.html. Although this talks in an exercise context, the principles are the same. I'm also told that depending on whether an individual is acid or alkaline based determines where you get your Vitamin C from.
Interestingly, except for my early morning apple, I don’t often eat fruit on its own, certainly not in large quantities. Perhaps this is why I have seen no change.
In future, I think I might keep some of the habits (e.g. less fruit juice, snack on rice cakes, natural yoghurt rather than the likes of Muller light) however I will not be omitting fruit from my diet, I believe the positives far outweigh the negatives. I also read that strength training is the best way to reduce body fat %. But I think that’s a topic for another blog, perhaps! And then there’s also the different fruits and how they have different fructose levels....
My conclusion: Science may suggest that fructose contributes to body fat, but science also suggests that it contributes in part to sports performance, stronger immune systems (as well as many other things I expect)! So where you gain in one area, you might lose in the other.
Melanie Ryding
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