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Not my belief but one I ran into over at health SE. Interested to see what data there is beyond my (and tyler's) findings.

Argument for: https://health.stackexchange.com/a/7648/5266 -dead link

Argument against: http://www.nature.com/ijo/journal/v37/n6/full/ijo2012157a.html

Argument made for amount of calories being the only factor:

Independent of your diet’s macronutrient ratios, a negative energy balance (consuming fewer calories than your body needs) is responsible for weight loss. (Examine.com)

Argument made against amount of calories being the only factor:

"Not all calories are created equally. The body has to expend different amounts of energy to digest different foods. For example, just looking at sugars alone, it is easier for the body to utilize glucose than fructose. Some foods are completely indigestible even though they have "calories". Also, some fat usually passes through the digestive tract and is not even digested at all"

Does the evidence support a strong causal relationship between (specifically) fructose consumption and obesity?

  • Regarding the "do different types of calory contribute different amounts towards weight gain" aspect of the question, I'm sure someone asked something similar earlier this year, can't find it right now though... ...here it is, looks like it was editted to specifically address heart disease only and sugar vs fats only, not different types of sugar, but some of the research is related – user56reinstatemonica8 Aug 3 '16 at 13:01
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    The primary effect contributing to weight/obesity is caloric intake. That not all calories are created equally statement is a secondary effect, that may decrease the primary effect but can never overtake it. The statement fructose is the #1 source of obesity can thus only be 'proven' if one shows that the bulk of our caloric intake is fructose. – user22865 Sep 23 '16 at 10:20
  • I'd argue that because physics exists as a science, all calories are created equally, provided they are calculated using the same method. – Gunge Sep 26 '16 at 7:07
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    @Jan unfortunately I cant see the original post, maybe a high rep user could find the old post and repost the comment? – Gunge Sep 27 '16 at 9:05
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    This doesn't seem to quite fit the SE format as you didn't provide a source saying that fructose is the #1 source. – Fizz Dec 25 '17 at 15:33
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+100

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 tested sweeteners.

Evidence:

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 the fructose.

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

Additional info:

  • Foods high in fructose: apples, pears, mangoes and several other fruits, agave, honey; HFCS sweetened beverages, sucrose (NutrientsReview)

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