Moderate Fructose Consumption Not Linked to Weight Gain

Summary
Some researchers have suggested that consumption of fructose leads to obesity; however, recently a review demonstrated that there was no relationship between consumption of normal dietary fructose and an increase in weight in normal weight individuals. Since the metabolic pathways are unstable in the obese, it is believed that fructose might be metabolized differently in obese individuals, and therefore their response to it might be different. This systematic review of high-quality published research failed to find an association between fructose intake and the level of triglycerides (the chemical form of fat found in most foods and your body) in blood or body weight in overweight or obese individuals.

Introduction
Fructose is a sugar naturally present in many fruits. It is also used as sweetener in beverages. The average daily intake of total fructose has increased from 37g/day in 1978 to 49g/day by 2004. This is mainly due to increased use of fructose as an ingredient in beverages and ready-to-eat products. During this same period, an increase in obesity, diabetes and heart diseases has also been noted. A recent review in healthy, normal weight humans indicates that after ingestion of moderate amounts of fructose, sucrose, glucose or starch, short increases in plasma triglycerides occur. However, no evidence suggests that ingestion of moderate amounts of fructose is associated with an increase in body weight in normal weight individuals. Because there is a large population that is overweight, a similar review in the obese population would be very useful.

Methodology
* A comprehensive search of the published literature was performed in SCOPUS (which is the largest abstract and citation database of research literature) for articles on this topic. PubMed was also searched for similar studies. Seventy-seven manuscripts matching our inclusion criteria were found. Using the FDA criteria for evidence-based research, 45 studies were considered to be of high quality and were included in this review.
* There were two kinds of studies, interventional and observational. In an intervention study, a quantity of the food supplement (fructose) was provided to subjects and effects were noted. Observational studies measured the association between the substance and disease.
* Studies were further categorized based on duration of intervention and whether they were carried in normal weight or obese patients.

Results
* In obese patients, consumption of 30 to 100g/day of fructose did not induce any significant rise in blood levels of triglycerides a short duration after consumption.
*  Long-term studies on normal weight and overweight subjects showed that there was no effect of up to 100g/day fructose on fasting blood levels of triglycerides.
* “Intake of normal amounts of fructose has the same effect on triglycerides or body weight in overweight or obese individuals as similar amounts of other carbohydrates such as glucose or sucrose.”

Next steps
In overweight and obese subjects with diabetes, the effects of fructose on blood glucose have been observed to be beneficial. This study suggests that fructose actually lowers glucose levels in the blood. Further research would establish whether moderate amounts of fructose could be recommended for such people. Amounts as high as 120g of fructose consumed daily showed no rise in blood triglyceride levels. But such empty calories may not be good for obese, hypertensive, diabetic or sedentary patients. Hence caution needs to be exercised.

Conclusion
Because a large percentage of the population is overweight or obese, it is of interest to conduct reviews on the association of various dietary constituents and obesity. Fructose consumption has increased significantly in the last few decades. Whether this is responsible for the epidemic of obesity, through an increased consumption and metabolism of fructose in the body, was the question addressed in this review. It is concluded that consuming a moderate amount (around 50g) of fructose daily will not have an adverse effect on body weight in overweight or obese humans. Fructose consumed at very high amounts, however, has been proven to affect weight gain.

For More Information:
Evidenced Based Review on the Effect of Normal Dietary Consumption of Fructose on Blood Lipids and Body Weight of Overweight and Obese Individuals
Publication Journal: Critical Reviews in Food Science and Nutrition, November 2010
By Laurie C. Dolan; Susan M. Potter; Burdock Group, Orlando, Florida, and the Tate & Lyle Health and Nutrition Sciences, Decatur, Illinois

*FYI Living Lab Reports Are Summaries of the Original Research.