Original Article

Conjugated linoleic acid (CLA) and obesity

Manuela-Belén Silveira^a1 c1, Raffaele Carraro^a1, Susana Monereo^a2 and Javier Tébar^a3

^a1 Servicio de Endocrinología y Nutrición, Hospital Universitario de La Princesa, Diego de León, 62. 28006 Madrid, Spain

^a2 Sección de Endocrinología y Nutrición, Hospital Universitario de Getafe, Madrid, Spain

^a3 Servicio de Endocrinología y Nutrición, Hospital Universitario Virgen de La Arrixaca, Murcia, Spain

Abstract

Background The term conjugated linoleic acid (CLA) refers to several positional and geometric conjugated dienoic isomers of linoleic acid (LA), of which the trans-10,cis-12 isomer has been reported to reduce adiposity and increase lean mass in mice and other animals when included at ≤1% of the diet. However, most dietary CLA in humans is obtained from dairy products, accounting for the cis-9,trans-11 CLA isomer, also known as rumenic acid, for more than 90% of the total CLA intake. Commercial CLA preparations industrially produced, containing trans-10,cis-12 and cis-9,trans-11 CLA isomers in diverse proportions, are attracting consumers’ interest because of the purported body fat-lowering effects of CLA, coupled to the perception of a ‘natural’ compound devoid of harmful effects. Nevertheless, despite numerous studies on CLA effects on body composition for nearly a decade, the mechanisms by which CLA isomers elicit their effects remain largely unknown. The purpose of this paper is to provide an updated review of the studies performed on animals and humans, as well as to describe the potential mechanisms involved in CLA effects on body weight and composition and metabolism.

Method Literature review.

Results Experiments in humans have not been able to show a significant effect on body weight, body composition or weight regain related to either of the CLA isomers. In fact, some studies suggest a tendency towards a decrease in body fat mass and an increase in body lean mass, while some others raise concern about the possibility of deleterious effects of trans-10,cis-12 CLA on lipid profile, glucose metabolism and insulin sensitivity.

Conclusions Evidence regarding effectiveness of CLA in humans is not concluding.

(Received November 2006)

(Accepted April 2007)

Keywords

• CLA fatty acid;
• Obesity;
• Anti-obesity agents;
• Body composition;
• Lipid metabolism;
• Insulin resistance;
• Diabetes mellitus type 2

Correspondence:

^c1 Corresponding author: Email belensilveira@telefonica.net