Can fructose (fruit sugar) make you fat? A personal eating experiment based on research seeks to find the answer.
A crude search on the internet to find out if fructose is in fact bad for you 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.” (Wikipedia)
There is some suggestion in the media that fructose could be more likely to store as fat, but would that only occur if you ate a large quantity of fruit? There was only one way to find out: I omitted it for two weeks. Here is what happened.
My rules for the no fructose diet
I constructed some basic rules that I could stick to in an attempt to try and eliminate variables and ensure my diet was as fructose free as possible. These are the steps I took:
- For two weeks, I consumed no fruit at all, including no fruit drinks and nothing fruit flavoured. I checked everything I ate for fructose content.
- I replaced fruit with rice cakes, small quantities of nuts, ham or something similar.
- I drank water instead of fruit drinks.
- I used no sports drinks or anything of that nature during week 1, and only once during week 2.
- I still planned to follow my 3-2-1 rules with regards to meal balance (breakfast as my main meal, a medium lunch and light tea; all training before breakfast)
- I still drank black coffee.
Was it Difficult to Eat Like This?
I found this type of diet exceptionally hard, harder than I thought it would be. I really missed and craved sweet things and 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, I would be tempted to choose a less healthy option because I craved the sweet taste.
Savoury snacks just simply did not satisfy my cravings. Even after the diet was over, I found that where I would normally crave fruit, my cravings switched to cakes and biscuits. When I first gave up chocolate, it took two 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 okay to eat biscuits and cakes because they are not fruit and it’s fruit I am not allowed. Of course, this is an irrational train of thought. Clearly, there is a real risk here to my well being, health, and training fuel mix.
At times, I also found that exercise was harder, and I felt a lot more lethargic during morning pre-breakfast training sessions. Some people say it was psychological, but I don’t think it was because this didn’t change at all throughout the weeks on the diet. I drank water instead of the usual energy drink and used Red Bull (which I disliked because it is carbonated), but found myself more fatigued, and had more muscle aches.
It is also worth noting this, the most important thing: During the experiment, I was ill in one way or another. First, I got an eye infection, and then no sooner was I clear when 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 was very glad to get back to my usual fruit-filled diet.
Results after two weeks on a no fruit diet
After two weeks of eating no fruit, the following occurred:
- I lost 2.5 pounds.
- My BMI dropped by 0.1.
- There was no change in my body fat percentage.
- There was no change in my water content percentage.
What does this mean?
My husband’s first reaction was that maybe because the conversion happens in my liver, the liver is skinnier, but that is all. I think big changes would be seen more in people who previously had a high fructose diet or an unbalanced diet that contained high volumes 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 conducted on subjects with a much higher body fat percentage in the first place, therefore my results cannot be deemed as conclusive.
Further research on fructose
After receiving some more research that was another challenge to this theory, I wondered why energy drinks contained fructose, if it had been proven to be so bad for you.
One personal website based source stated that fat is a poor fuel that makes you go slower, but also talked about fat burning and weight management, embracing the “train before breakfast” idea that I already do. They state that training in this way will not yield results but is a weight management tool.
Another, however, talked about fuel for performance, and suggested that despite fruit sugar being bad, a glucose/fructose combination is actually good for you with regards to sports performance.
The latest research on carbohydrate recommendations during exercise by Tricia Griffin says “research indicates that glucose and fructose have their own separate transport systems in the digestive tract. ..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.”
Other people’s views on fructose
I tried to understand why the research suggests that fructose may be more likely to convert to fat, yet I had seen no change. A nutritional advisor I know reminded me that it may take up to 12 weeks to see a change, much like when you first start exercising. It is also worth noting that everybody is different, therefore the results will not be the same for everyone that tries this.
Many people have said that surely the benefits of fruit outweigh everything else. I tend to agree. I was sent some literature, which, although the research was still in very early stages, is suggesting that polyphenols and flavanoids (found particularly in fruit) are key to rebuilding muscle. This could why I ached so much more than normal.
Lagouge conducted a study on mice in 2006, which proved that resveratrol can help prevent diet-induced obesity as well as increasing oxygen intake and aerobic capacity.
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 found another quote that says exactly that; fruit and vegetables stave off other cravings. But people are still saying excessive fructose consumption is bad for you.
Information from Dr. Cordain’s article on reducing triglycerides says that fructose, especially its excessive consumption, may increase:
- risk of type 2 diabetes
- LDL bad” cholesterol levels
- irregular bowel habits (diarrhoea)
- risk of obesity
I do not, however, believe that I excessively consume fructose.
What now for me?
I am told by local nutritionists that eating fructose-based foods with protein slows down conversion to glucose and regulates the release of insulin. Insulin is needed to properly utilize the energy stored in carbohydrate. 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 the future, I think I might keep some of the habits (for example, drink less fruit juice, snack on rice cakes and 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.
Science may suggest that fructose contributes to body fat, but science also suggests that it contributes in part to sports performance and stronger immune systems, as well as many other things). Where you gain in one area, you might lose in the other.
Disclaimer: The information contained in this article is for educational/entertainment purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
- Griffin, T ‘Carbohydrate recommendations during exercise’ [online – available http://www.powerbar.com/articles/18/latest-research-on-carbohydrate-recommendations-during-exercise.aspx]
- Lagouge, M et al (2006) ‘Resveratrol Improves Mitochondrial Function and Protects against Metabolic Disease by Activating SIRT1 and PGC-1α’ Cell, 15 December 2006 (Vol. 127, Issue 6, pp. 1109-1122)
- Cordain, L (2011) triglycerides-lowering diet: What about Fructose?’ Fruit and Sugar Content: The Paleo Diet [online, available http://www.reducetriglycerides.com/reader_triglycerides_low_fructose_fruit.htm]