Sugar-fat seesaw: a systematic review of the evidence
Sadler,M.J., McNulty,H.M. and Gibson,S.,(2013) Crit Rev Food Sci Nutr 10.1080/10408398.2011.654013
Objective: To examine the relationships between sugars and fat as expressed as % energy and in absolute terms. In addition, to examine if any relationship is applicable to the general population, evidence of any threshold effect, and the relationship to particular types of fatty acid and other macronutrients and fibre.
Design: Systematic review.
Main outcome measures: Examined associations between total sugars and total fat intakes, sugar sub-types and total fat, sugar and types of fats, sugars and other macronutrients or alcohol. Also examined the effect of intervention trials to increase/decrease sugar/fat on the relationship.
Results: Studies revealed a consistent inverse association between intakes of sugars and fat expressed as % energy across all population groups. This inverse relationship also existed for extrinsic sugars although the evidence was less consistent. The few studies which examined the relationship on the basis of absolute intakes, reported a positive relationship. However, when this relationship was adjusted for energy intake it became inverse.
The same relationship existed between total and extrinsic sugars and protein - i.e. inverse association when expressed as % energy, positive relationships when expressed in absolute terms, but inverse when adjusted for energy.
There was also evidence of inverse association between total or extrinsic sugars and starch, extrinsic sugars and fibre, sugars and alcohol.
No evidence that high-sugar high-fat foods explained the sugar-fat intake relationship i.e. foods high in sugars are generally low in fat and vice-versa.
Interventions studies supported the inverse relationship between fat and sugars when expressed as %energy, but the evidence was equivocal when expressed in absolute terms.
Conclusions: This research confirms the existence of a sugar-fat seesaw on a % energy basis. Population dietary guidelines are expressed in terms of % energy and therefore the results imply that conforming to % energy guidelines to reduce both fat and sugar may be difficult in practice. Absolute intakes may be more important at the individual level.
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