Fructose is a natural component, a monosaccharide found naturally in fruit, vegetables, honey and is also found in breast milk.
It has very few calories, only 4 kcal per gram and is used as a sugar substitute in the food industry.

It is to be consumed in moderation because the chronic intake of fructose has important contraindications.

Excessive fructose consumption has been linked, at least partially, to greater adiposity and metabolic disorders compared to other sugars that seem to be particularly important during critical periods of growth and infant development (1).

Excessive consumption of fructose has been linked, at least partially, to increased adiposity and metabolic disturbances compared with other sugars that seem to be particularly important during critical periods of childhood growth and development (2).

References_____________________________________________________________________

(1) Welsh, J.A.; Sharma, A.; Cunningham, S.A.; Vos, M.B. Consumption of added sugars and indicators of cardiovascular disease risk among US adolescents. Circulation. 2011 Jan 25;123(3):249-57. doi: 10.1161/CIRCULATIONAHA.110.972166. 

Abstract. Background: Whereas increased carbohydrate and sugar consumption has been associated with higher cardiovascular disease risk among adults, little is known about the impact of high consumption of added sugars (caloric sweeteners) among US adolescents. Methods and results: In a cross-sectional study of 2157 US adolescents in the National Health and Nutrition Examination Survey (NHANES) 1999 to 2004, dietary data from one 24-hour recall were merged with added sugar content data from the US Department of Agriculture MyPyramid Equivalents databases. Measures of cardiovascular disease risk were estimated by added sugar consumption level (< 10%, 10 to < 15%, 15 to < 20%, 20 to < 25%, 25 to < 30%, and ≥ 30% of total energy). Multivariable means were weighted to be representative of US adolescents and variances adjusted for the complex sampling methods. Daily consumption of added sugars averaged 21.4% of total energy. Added sugars intake was inversely correlated with mean high-density lipoprotein cholesterol levels (mmol/L) which were 1.40 (95% confidence interval [CI] 1.36 to 1.44) among the lowest consumers and 1.28 (95% CI 1.23 to 1.33) among the highest (P trend = 0.001). Added sugars were positively correlated with low-density lipoproteins (P trend =0.01) and geometric mean triglycerides (P trend = 0.05). Among the lowest and highest consumers, respectively, low-density lipoproteins (mmol/L) were 2.24 (95% CI 2.12 to 2.37) and 2.44 (95% CI 2.34 to 2.53), and triglycerides (mmol/L) were 0.81 (95% CI 0.74, 0.88) and 0.89 (95% CI 0.83 to 0.96). Among those overweight/obese (≥ 85th percentile body-mass-index), added sugars were positively correlated with the homeostasis model assessment (P linear trend = 0.004). Conclusion: Consumption of added sugars among US adolescents is positively associated with multiple measures known to increase cardiovascular disease risk.

(2) Goran, M.I.; Dumke, K.; Bouret, S.G.; Kayser, B.; Walker, R.W.; Blumberg, B. The obesogenic effect of high fructose exposure during early development. Nat Rev Endocrinol. 2013 Aug;9(8):494-500. doi: 10.1038/nrendo.2013.108.

Abstract. Obesogens are compounds that disrupt the function and development of adipose tissue or the normal metabolism of lipids, leading to an increased risk of obesity and associated diseases. Evidence for the adverse effects of industrial and agricultural obesogens, such as tributyltin, bisphenol A and other organic pollutants is well-established. Current evidence suggests that high maternal consumption of fat promotes obesity and increased metabolic risk in offspring, but less is known about the effects of other potential nutrient obesogens. Widespread increase in dietary fructose consumption over the past 30 years is associated with chronic metabolic and endocrine disorders and alterations in feeding behaviour that promote obesity. In this Perspectives, we examine the evidence linking high intakes of fructose with altered metabolism and early obesity. We review the evidence suggesting that high fructose exposure during critical periods of development of the fetus, neonate and infant can act as an obesogen by affecting lifelong neuroendocrine function, appetite control, feeding behaviour, adipogenesis, fat distribution and metabolic systems. These changes ultimately favour the long-term development of obesity and associated metabolic risk.