These days you can hardly watch a T.V. program without being bombarded by the newest diet craze. Maybe it’s the time of year, January, when everyone is hoping to make 2018 their year, but more likely it is because dieting has become a multi-billion-dollar industry in the United States.


As a new-ish mother I’ve been carrying around the last 5, 10, okay 15 pounds for the last 7 months and decided in a sleep deprived haze to attempt a weight loss intervention for 2018. I was immediately overwhelmed by the number of programs, quick fixes, and suspicious non-FDA approved ‘supplements’ floating around on the market.


While all of these diets certainly have their individual gimmicks, they center around the core idea of calories in vs calories out. This core tenant of weight loss has been recognized as the hallmark of successful lifestyle change, that is, to lose weight one must intake less energy than they expend. While there are multiple ways to achieve this negative energy balance (i.e. diet, exercise, weight loss surgery, pharmaceuticals, etc.) I was interested in how to achieve negative balance while retaining a healthy breastmilk supply.


Breastmilk is composed of the 3 major macronutrients: fat, protein, and carbohydrate. Of these, mature breastmilk (that produced around day 6), contains 3.5 g of fat, 7 g of carbohydrate, and 0.9 g protein per 100ml. It also contains a whole host of other vitamins, minerals, immunoglobulins, and bioactive factors (1).  Most of the papers examining breastmilk composition in well controlled studies focus on diversity and amount of specific Fatty Acids, total protein profile, and total energy content (2). Multiple studies have also focused on the amount of DHA passed in breastmilk and linked it to maternal consumption of fatty fish (2).


While the outcomes of these studies showed associations of maternal diet with breastmilk composition only one well controlled study has been done to address the effects of following a diet (low carbohydrate or low fat) on the composition and supply of breastmilk. This study found that under moderate caloric restriction women on a ‘low’ (~31%) carbohydrate diets (vs low fat diets ~26% fat) had higher levels of fat in their breastmilk with higher levels of energy expenditure. Neither diet impacted breastmilk production as both were only moderately hypocaloric (3).

So where does that leave us?


We know women are likely to gain and retain weight during a first pregnancy putting them at higher risk for complications should a second pregnancy be desired. It appears that the most important time for weight loss interventions is the first 18 months post-partum after which weight loss tends to plateau (4). With the importance of exclusively breastfeeding up to a year we need more studies that focus on effective weight loss techniques for post-partum women who wish to maintain milk supply.


As for me? I think I’ll cut out the bread and leave the butter.





1) World Health Organization. “Infant and young child feeding: model chapter for textbooks for medical students and allied health professionals.” (2009).


2) Bravi, Francesca, et al. “Impact of maternal nutrition on breast-milk composition: a systematic review, 2.” The American journal of clinical nutrition 104.3 (2016): 646-662.


3) Mohammad, Mahmoud A., Agneta L. Sunehag, and Morey W. Haymond. “Effect of dietary macronutrient composition under moderate hypocaloric intake on maternal adaptation during lactation–.” The American journal of clinical nutrition 89.6 (2009): 1821-1827.


4) Gunderson, Erica P. “Childbearing and obesity in women: weight before, during, and after pregnancy.” Obstetrics and Gynecology Clinics 36.2 (2009): 317-332.