Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/11/2008
Publication Date: 4/22/2009
Citation: Mohammad, M.A., Sunehag, A.L., Haymond, M.W. 2009. Effect of dietary macronutrient composition under moderate hypocaloric intake on maternal adaptation during lactation. American Journal of Clinical Nutrition. 89(6):1821-1827. Interpretive Summary: No recommendations exist concerning what diet optimizes weight loss during lactating while maintaining milk production for the infant. This study tests various diets. The study concluded that under moderate calorie restriction, low carbohydrate/high fat diet did not decrease milk production; otherwise, it increased milk fat, milk energy output and resting energy expenditure. Therefore, the low carbohydrate/ High fat diet resulted in a greater energy utilization without adversely affecting milk production or composition. Long-term studies are mandatory to determine whether a low calorie, low carbohydrate /high fat diet might promote weight loss while maintaining successful breastfeeding.
Technical Abstract: No evidence-based recommendations exist concerning what dietary macronutrient composition optimizes weight loss during lactation while maintaining milk production. This study was designed to test the following hypotheses: compared to a reduced-calorie, high-carbohydrate (H-CHO) diet, an isonitrogenous, isocaloric high-fat (H-F) diet will decrease milk production and carbohydrate oxidation, increase gluconeogenesis and hexoneogenesis, and not affect energy balance. Seven healthy lactating mothers and their infants were studied on 2 occasions in random order for 8 days separated by 1-2 weeks. On one occasion, the subjects received the H-F (30% of energy as carbohydrate and 55% as fat) diet and on the other occasion received the H-CHO (60% of energy as carbohydrate and 25% as fat) diet. Milk production, infant intakes, and substrate and hormone concentrations were measured. Glucose rates of appearance, production, gluconeogenesis, glycogenolysis, and hexoneogenesis were measured by using stable-isotope gas chromatography-mass spectrometric techniques, and energy expenditure and substrate oxidation were measured by using indirect calorimetry. Our results showed that milk volume, lactose, and protein concentrations were unaffected. Milk fat, energy, and infant intakes were higher (P < 0.05) during the H-F diet. Neither gluconeogenesis nor hexoneogenesis was different. During the H-F diet, energy expenditure and fat and protein oxidation rates were higher (P < 0.05) and the daily energy balance deficit was greater (P < 0.01). Milk fat, energy output, and energy expenditure were higher during the H-F diet, which resulted in a greater negative energy balance. The lactating mothers adapted to a low carbohydrate intake by decreasing carbohydrate oxidation. Additional studies are warranted to determine whether a hypocaloric H-F diet might promote weight loss to a greater extent than the H-CHO diet while maintaining milk production.