Can fructose consumption be linked to visceral fat? The answer, according to a new study (1) which investigated the effects of fructose consumption on health, is yes.
The study, published by the American Society of Nutrition examined the relationship between fructose consumption and cardiometabolic risk among adolescents, whose fructose consumption is higher than other groups. This is not because of their love for fresh fruit of course, but their high intakes of sweetened foods and beverages which use fructose or high fructose corn syrup (HFCS) to enhance taste.
In this study of 559 adolescents aged 14-18, fasting blood samples were collected for glucose, insulin, lipid, adiponectin, and C-Reactive protein. Diet was assessed with 4-7 24h recalls and physical activity was determined by use of accelerometry. Fat mass and lean body mass were measured using a DXA scan. Visceral fat (the fat beneath the muscles compacted around the organs) was measured as was subcutaneous fat (fat beneath the skin)
The results showed that fructose consumption was associated with visceral fat but not subcutaneous fat. In addition there was a linear relationship between increasing fructose intakes and systolic blood pressure and fasting glucose which could present risks for an increased susceptibility to diabetes or cardiac events. By contrast, there was a trend for rising intakes of fructose being associated with lowered HDL cholesterol and adiponectin levels which are important for health and weight loss respectively. In fact, adiponectin, a type of protein hormone, has an inverse relationship with body fat percentage, with low adiponectin levels being associated with high bodyfat and other health related issues (2).
The authors concluded that higher fructose consumption was positively correlated with increased risk on multiple markers of cardiometabolic risk which could be due to the impact of increased visceral fat deposition seen in those consuming fructose at higher doses.
For some time bodybuilders have been wary of the consumption of fructose in the belief that it cannot be used by muscle glycogen and is only useful for replenishing liver glycogen levels with an excessive amount easily converted into body fat. A number of studies have been conducted on fructose which highlights its potential to cause insulin resistance, obesity and metabolic syndrome. As a consequence, despite its low glycaemic index, it is generally not advised to be consume liberally. Indeed, large doses of fructose are associated with liver damage said to be equivalent to that seen in alcoholics (3).
Of greater concern to us athletes is what level of fructose is advisable to consume. First, we need to remember that it is almost impossible to consume pure fructose as even fruits and HFCS contain plenty of glucose. In fact, the much demonised HFCS is nearly identical to table sugar (sucrose) in terms of its ratio of glucose to fructose. Sucrose is 50/50 while HFCS is about 55/45. Although some studies show that fructose intake does not increase leptin or satiate appetites, there is other data to show that a fructose preload can lead to lower caloric consumption than a glucose preload in a subsequent meal (4). At the same time, excessive fructose consumption in one study led to greater food consumption the following day (6) but this was at a dose of 135 grams of pure fructose which would be very high indeed for the average person (equivalent to about 7 soft drink cans per day).
The take home message here is that excessive fructose consumption should be avoided. Generally speaking, it is always good advice to focus diet around minimally processed foods as they will be the healthiest for us. A daily fructose consumption of around 50 grams per day for athletes should be fine and plenty enough to replenish liver glycogen and also ensure we get the health benefits of fructose. If we focus our fructose intake on fruits which tend to be only around 50% fructose then it is very unlikely we run into any problems with health.
1. Pollock et al (2012): Greater Fructose Consumption Is Associated with Cardiometabolic Risk Markers and Visceral Adiposity in Adolescents
2. Ukkola O et.al (2002): Adiponectin: a link between excess adiposity and associated comorbidities?
3. Ouyang X et.al (2008): Fructose consumption as a risk factor for non-alcoholic fatty liver disease.
4. Monsivais et.al Sugars and Satiety (2007) Does the type of sweetener make a difference.
5. Rodin et.al Metabolic effects of fructose and glucose: Implications for food intake
6. Teff KL, et al. Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women. J Clin Endocrinol Metab. 2004 Jun;89(6):2963-72.
© 2012, Reggie Johal. All rights reserved.