Question: "Does the evidence support a strong causal relationship between (specifically) fructose consumption and obesity?"
My answer: NO.
Consideration 1: This question has arisen because of "simultaneous" increase of use of high-fructose corn syrup (HFCS) and obesity in the United States.
Consideration 2: There has been some debate if fructose increases appetite. According to American Journal of Clinical Nutrition, 2008, it may not:
Insufficient scientific evidence currently exists to indicate that
HFCS...increases short-term appetite and energy intake more than do other
1. Effect of fructose on body weight in controlled feeding trials: a systematic review and meta-analysis (PubMed, 2012)
Fructose does not seem to cause weight gain when it is substituted for
other carbohydrates in diets providing similar calories. Free fructose
at high doses that provided excess calories modestly increased body
weight, an effect that may be due to the extra calories rather than
2. Misconceptions about fructose-containing sugars and their role in the obesity epidemic: literature review (PubMed, 2014)
Current evidence on the metabolic effects of fructose, as consumed by
the majority of populations, is insufficient to demonstrate such a
role in metabolic diseases and the global obesity epidemic.
3. Fructose Metabolism and Relation to Atherosclerosis, Type 2 Diabetes, and Obesity (PubMed Central, a review article 2015)
Current literature does not indicate that a normal consumption of
fructose (approximately 50–60 g/day) increases the risk of ...obesity
more than consumption of other sugars.
4. Calories listed on the Nutrition Facts labels represent "physiologically available energy, which is the energy value remaining after digestive and urinary losses" (USDA.gov, p. 14). If you additionally eliminate the part of energy used for heat, you get "net metabolic energy (NME)," which, if in excess of body needs, results in weight gain. According to the table 3 from EJCN, 2007; fructose has one of the lowest net metabolizable energies (NME) among digestible carbohydrates:
- Glucose (dextrose) monohydrate: 14.1 kJ or 3.4 Cal/g
- Fructose: 15.2 kJ or3.6 Cal/g
- Glucose: 15.7 kJ or 3.7 Cal/g
- Lactose: 16.3 kJ or 3.9 Cal/g
- Sucrose: 16.3 kJ or 3.9 Cal/g
- Starch: 17.5 kJ or 4.2 Cal/g
- Foods high in fructose: apples, pears, mangoes and several other fruits, agave, honey; HFCS sweetened beverages, sucrose (NutrientsReview)