A Cochrane review included 12 studies with a total of 910 women. Women who took part in a diet (WMD –1.70 kg, 95% CI –2.08 to –1.32; 1 study, n = 45) or diet plus exercise programme (WMDWMD -1.93 kg; 95% CI -2.96 to -0.89; 7 studies, n = 573, I² = 71%) lost significantly more weight than women in the usual care. The nutritional interventions included dietary advice, individualised dietary counselling, or prescription of a calorie-restricted diet. Exercise interventions were exercise counselling or structured exercise programmes. There was no difference in the magnitude of weight loss between diet and diet plus exercise group (WMD 0.30 kg, 95% CI –0.60 to 0.66; 1 study, n = 43). However, it seems preferable to lose weight through a combination of dieting and exercise to dieting alone because exercise compared to usual care improves cardiorespiratory fitness level (WMD in VO2max 6.73 ml/kg/minute, 95% CI 4.28 to 9.17; 4 studies, n = 90) and preserves fat-free mass (WMD –0.20 kg, 95% CI –0.67 to 0.27; 2 studies, n = 84), while diet alone compared to usual care reduces fat-free mass (WMD –0.90 kg, 95% CI –1.38 to –0.42; 1 study, n = 45;). Exercise alone did not increase weight loss compared to the usual care (WMD 0.00 kg, 95% CI –8.63 to 8.63; 1 study, n = 33). The interventions seemed not to affect breastfeeding performance adversely.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment and lack of blinding in half of the studies and inconsistency (heterogeneity in interventions and outcomes). For women who are breastfeeding, more evidence is required to confirm whether diet or exercise, or both, is not detrimental for either mother or baby.