Fructose, but not glucose, found to reduce fat-burning and metabolic rate

There’s no doubt about it, fructose has got itself an increasingly bad reputation in nutritional circles over the last few years, and has been linked with all sorts of ills including obesity, type 2 diabetes and an increased risk of heart disease. This week saw the publication of a study which further points a finger of suspicion towards fructose.

This particular study pitted fructose against glucose [1], and is reminiscent of another study I wrote about in June here which found that fructose, weight for weight, worsened disease markers more than glucose. This more recent research involved feeding overweight and obese men and women fructose- or glucose-sweetened drinks for 10 weeks. Total amount of sugar represented 25 per cent of total energy requirements. So, someone who typically consumes 2,000 calories a day would have consumed 500 calories-worth or 125 grams of sugar.

The study participants were assessed with a range of measurements including:

  1. fat oxidation (metabolism) after eating
  2. resting energy expenditure (basal metabolic rate)

The results showed that consuming fructose led to a significant reduction in both fat oxidation after eating and resting energy expenditure. These reductions were not, however, seen with glucose consumption. These findings suggest that, gram for gram, fructose has more fattening potential than glucose.

Admittedly, the amount of fructose consumed in this experiment was quite large (roughly equivalent to 3 cans each day or soda/soft drink). Nevertheless, the study does provide further evidence that fructose can harm health, and is generally more damaging in this respect than glucose.

References:

1. Cox CL, et al.Consumption of fructose-sweetened beverages for 10 weeks reduces net fat oxidation and energy expenditure in overweight/obese men and women. European Journal of Clinical Nutrition advance online publication 28 September 2011

12 Responses to Fructose, but not glucose, found to reduce fat-burning and metabolic rate

  1. leonardo 29 September 2011 at 2:18 pm #

    Does the same apply if the fructose is in the form of ‘real’ fruit?

    Which makes me think that to obtain the equivalent amount of fructose from fruit as 3 cans of soda, you would need to live near a plantation!

  2. Chris 29 September 2011 at 4:36 pm #

    “Admittedly, the amount of fructose consumed in this experiment was quite large (roughly equivalent to 3 cans each day or soda/soft drink).”

    3 by 330ml cams equates to 990ml. I have come across individuals who may consume 1.5l – 3.0l in the course of a day. These people may not represent a high proportion of consumers but in a social context their numbers would be significant.

  3. xtrocious 30 September 2011 at 12:27 am #

    I think 3 x 330ml cans are easily doable by most people, which is quite scary…

    In Singapore, more and more restaurants throw in “free flow” of soda to entice diners to patronise them…

    While we know better that soda is bad for us, most other diners will guzzle the soda with their meals…

  4. Justmeint 30 September 2011 at 7:46 am #

    Having a sweet tooth and disliking most calorie low alternative sweetners… I used to take 2 teaspoons of suger per cup of tea/coffee. I changed over a year ago to using one teaspoon of pure glucose and one sachet of stevia……. everyone warned me that the glucose would do damage and cause me to become diabetic…… WRONG….. my A1c’s are in perfect range and my weight dropped off a little and now remains stable.

    I have read much about the danger of so called healthy fruit sugars…. and ONLY get them now when I consume a piece of whole fruit.

    Regular table sugar is 50/50 glucose with fructose which equals what we call sucrose. Even a small reduction like I have done seems to have benefits.

  5. DaveHy 30 September 2011 at 6:34 pm #

    Does this mean eating fruit is bad for you? Are we better off eating chocolate?

  6. David Manovitch 1 October 2011 at 12:35 am #

    I suspect that any sugar, isolated and purified and eaten in more than minute quantities wil be bad for health. wse are surely intended to eat fruit, a major source of fructose, and I know of no evidence that suggests fruit to be bad for humans.Sucrose and glucose are les likely to be consumed in natural foods. Who would eat sugar cane for instance?

    Stick to whole unprocessed foods and all should be well. I personally use occasional small quantities of pure fructose to sweeten foods, because I suffer reactive hypoglycaemia if I ingest much sucrose or glucose. Generally I avoid the desserts, cakes, biscuits etc.

  7. Ian 1 October 2011 at 3:31 pm #

    Maybe we evolved to eat fruit. But fruit is a seasonal product, in this part of the world it’s only available for a few months each year.

    There is a school of thought that fruit evolved to increase our fat stores over the winter, and increase chances of survival.

    So, in our modern day society, if we eat it all year round, we just steadily get fatter and fatter.

  8. Elena 3 October 2011 at 6:49 am #

    Wow Ian. Good point. I’ve never thought of that!

  9. Richard David Feinman 5 October 2011 at 1:06 am #

    I have not looked at this study but the key question is what is the total carbohydrate intake. Most of the recent ones study, like Stanhope, 55 % carbohydrate diet against which they compare fructose and glucose. We would all stipulate that if you have a high carb diet you might be better off with replacing fructose with glucose but this is setting things up to get the answer the granting agency wants. Fructophobia is a ploy for not facing low carb. The surprising thing is how weak the actual results are. No effect of replacing fructose with glucose has ever been as strong as the effect of replacing any kind of carbohydrate with fat, even saturated fat. As I say, I haven’t read this one and it may be different but I’m guessing they studied a high carb diet.
    I made some comments on this on: http://wp.me/p16vK0-6W

  10. Kirsty 5 October 2011 at 11:09 am #

    Ian – really interesting point. I’ve never been a big fan of fruit but at the end of summer I usually go through a few weeks of really liking fruit (especially strawberries and other berries). I stopped eating grains three years ago and recently stopped regular dairy. This year my late summer fruit craze was especially noticeable. By this time of year it’s already passed.

    To be a bit pedantic, I don’t think fruit would have evolved to increase our fat stores but maybe we evolved to take advantage of what’s available seasonally.

  11. Mike Ellwood 24 January 2012 at 12:10 am #

    Just a small point, to say that the sugar in fruit is by no means all fructose (despite the name being derived from the Latin for fruit). Check a range of fruits (e.g. grapes, watermelons, oranges, peaches) and you will find they consist of some fructose, some glucose, and (usually) a small amount of sucrose. When you work it out, some have a little more fructose than glucose, some have a little more glucose than fructose, but it’s still not far off 50:50, like table sugar (refined sucrose). Admittedly, with apples and pears, I happened to notice that it’s more like 70:30, but it’s nowhere near 100% fructose. (See the USDA nutrient database).

    HFCS on the other hand, is quite a different matter. It is not a real food or a natural produce, and despite what we are often told, it is not equivalent to sucrose. But let’s not lay all the ills of HFCS at the door of fructose: it’s not justified.

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