Fructose, a natural sugar found in many fruits, it is sweeter than glucose or sucrose and is therefore commonly used as a bulk sweetener.

An increase in high fructose corn syrup, as well as total fructose, consumption over the past 10 to 20 years has been linked to a rise in obesity and metabolic disorders  This raises concerns regarding the short and long term effects of fructose in humans.

This paper reviews evidence in the context of current research linking dietary fructose to health risk markers.

Fructose intake has recently received considerable media attention, most of which has been negative. The assertion has been that dietary fructose is less satiating and more lipogenic than other sugars. However, no fully relevant data have been presented to account for a direct link between dietary fructose intake and health risk markers such as obesity, triglyceride accumulation and insulin resistance in humans.

First: a re-evaluation of published epidemiological studies concerning the consumption of dietary fructose or mainly high fructose corn syrup shows that most of such studies have been cross-sectional or based on passive inaccurate surveillance, especially in children and adolescents, and thus have not established direct causal links. Second: research evidence of the short or acute term satiating power or increasing food intake after fructose consumption as compared to that resulting from normal patterns of sugar consumption, such as sucrose, remains inconclusive. Third: the results of longer-term intervention studies depend mainly on the type of sugar used for comparison. Typically aspartame, glucose, or sucrose is used and no negative effects are found when sucrose is used as a control group.

Negative conclusions have been drawn from studies in rodents or in humans attempting to elucidate the mechanisms and biological pathways underlying fructose consumption by using unrealistically high fructose amounts.

The issue of dietary fructose and health is linked to the quantity consumed, which is the same issue for any macro- or micro nutrients. It has been considered that moderate fructose consumption of ≤50g/day or ~10% of energy has no deleterious effect on lipid and glucose control and of ≤100g/day does not influence body weight. No fully relevant data account for a direct link between moderate dietary fructose intake and health risk markers.

Fructose consumption and body weight

Lipogenesis from fructose consumption may theoretically be greater than that induced after eating other types of sugars such as glucose and sucrose. But could this be physiologically true?......

The effects of fructose on body weight were further questioned. When rats were fed a high fructose diet (60%) for 6 months then switched to a high fat diet for 2 weeks, leptin levels increased and a state of leptin resistance was found prior to increased adiposity and body weight induced by the high fat diet
 However, in other shorter term studies (3-6 weeks) high fructose feeding (57% in weight) induced insulin resistance and hypertriglyceridemia in rats but failed to induce an increase in body weight.

Thus, in rodents while excessively high fructose intake may increase appetite by different mechanisms, its' effect on body weight needs long term dietary periods.

Fructose and glucose metabolism in liver cells: 
After several steps glucose is converted into fructose1,6-bi-phosphate. A reaction regulated by the rate-limiting enzyme phosphofructokinase, which is inhibited by ATP and citrate. Altogether the conversion of glucose to pyruvate is regulated by insulin. On the other hand, 
fructose, is massively taken by the liver, and converted rapidly to triose-phosphate independently of insulin control and without a feedback by ATP or citrate. A large portion of fructose is converted into glucose which can be released in the blood or stored as glycogen. A part is converted into lactate. A small portion is converted into fatty acids, which may play an important role in the development of hypertriglyceridemia and fatty liver.

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Note : Recent study review that Fructose, a natural sugar found in many fruits, if consumed in significant amounts may caused obesity, fatty liver and other health risks.

Recommended take small portion at a time, consume whole fruit instead of fruit juice or processed fruits.