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Is it worth advising obese people to try a low-GI diet?

Summary of a Cochrane review that could be relevant to your next consultation

Summary of a Cochrane review that could be relevant to your next consultation

What is the evidence that low glycaemic index (GI) diets are any better than other weight reduction diets?

Obesity is increasingly prevalent, yet nutritional management strategies remain contentious. It has been suggested low glycaemic index or load diets may stimulate greater weight loss than higher glycaemic index or load diets or other weight reduction diets.

In this review we assessed the effects of low glycaemic index or load diets for weight loss in overweight or obese people.


Trials were identified through The Cochrane Library, MEDLINE, EMBASE, CINAHL and manual searches of bibliographies. Randomised controlled trials compared a low glycaemic index or load diet (LGI) with a higher glycaemic index or load diet or other diet (Cdiet) in overweight or obese people.

Two authors independently selected trials, assessed quality and extracted data, including any information provided on adverse effects.


We identified six eligible randomised controlled trials involving a total of 202 participants. Interventions ranged from five weeks' to six months'' duration with up to six months' follow-up after the intervention ceased.

The decrease in body mass (weighted mean difference-1.1 kg, 95% confidence interval (CI) -2.0 to -0.2, P < 0.05) (n = 163), total fat mass (WMD -1.1 kg, 95% CI -1.9 to -0.4, P < 0.05) (n =147) and body mass index (WMD -1.3, 95% CI -2.0 to -0.5, P < 0.05) (n = 48) was significantly greater in participants receiving LGI compared with Cdiets.

The decrease in total cholesterol was significantly greater with LGI compared with Cdiets (WMD -0.22mmol/l, 95% CI -0.43 to -0.02, P < 0.05), as was the change in LDL-cholesterol (WMD -0.24mmol/l, 95% CI -0.44 to -0.05, P < 0.05). No study reported adverse effects, mortality or quality of life data.

Authors' conclusions

Overweight or obese people on LGI lost more weight and had more improvement in lipid profiles than those receiving Cdiets. Body mass, total fat mass, body mass index, total cholesterol and LDL-cholesterol all decreased significantly more in the LGI group.

In studies comparing ad libitum LGI diets with conventional restricted energy low-fat diets, participants fared as well or better on the LGI diet, even though they could eat as much as wanted.

Lowering the glycaemic load of the diet appears to be an effective method of promoting weight loss and improving lipid profiles and can be simply incorporated into a person's lifestyle.

Further research with longer-term follow-up will determine whether improvement continues long-term and improves quality of life.


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