Did my milk supply go down because I am underweight?

Being severely malnourished may prevent mothers from establishing or maintaining their milk supply and may also decrease the quality of the milk.  

A) Causes of malnutrition

A severely malnourished mother may:

  • Have anorexia nervosa, an eating disorder characterized by low food intake.
  • Practice extreme dieting.
  • Be suffering from starvation.
  • Have major weight loss caused by
  • May be missing certain critical vitamins or minerals.
  • Weigh significantly less than expected.

Mothers with eating disorgers may be more likely to worry about the baby’s milk intake and feeding patterns. Such anxiety can interfere with breastfeeding and indeed, with the baby’s entire feeding environment (Kaß 2021; Kimmel 2016). 

B) The effects of being malnourished on breastfeeding

Many mothers unnecessarily worry that a poor diet will affect the quality or quantity of their milk. However only severe malnutrition, a lack of proper nutrition, can have this effect (Taneja 2021). When mothers are severely malnourished: 

  • The milk supply may be low from birth or reduced (Brown 1992; Horie 2017; Huynh 2018).
  • They are more likely to stop breastfeeding early (Chen 2020).
  • The milk may not have enough calories or protein (Dewey 1997).
  • The milk may be lacking in particular components such as vitamin B12, iron, zinc, and iodine. 

Drinking more water or other liquids will not affect the milk supply unless the mother is severely dehydrated as when sick from severe vomiting or diarrhea. Mothers only need to drink to settle their thirst.


Brown KH, Dewey KG. Relationships between maternal nutritional status and milk energy output of women in developing countries. In: Mechanisms Regulating Lactation and Infant Nutrient Utilization (Picciano MF and Lonnerdal B, eds.), pp. 77-95. Wiley-Liss: New York, 1992

Chen CN, Yu HC, Chou AK. Association between Maternal Pre-pregnancy Body Mass Index and Breastfeeding Duration in Taiwan: A Population-Based Cohort Study. Nutrients. 2020 Aug 7;12(8):E2361
Dewey KG. Energy and protein requirements during lactation. Annual Review of Nutrition 17:19-36, 1997
Horie S, Nomura K, Takenoshita S, et al. A relationship between a level of hemoglobin after delivery and exclusive breastfeeding initiation at a baby friendly hospital in Japan. Environ Health Prev Med. 2017 Apr 20;22(1):40
Huynh DTT, Tran NT, Nguyen LT, et al. Impact of maternal nutritional supplementation in conjunction with a breastfeeding support program on breastfeeding performance, birth, and growth outcomes in a Vietnamese population. J Matern Fetal Neonatal Med. 2018 Jun;31(12):1586-1594 

Kaß A, Dörsam AF, Weiß M, Zipfel S, Giel KE. The impact of maternal eating disorders on breastfeeding practices: a systematic review. Arch Womens Ment Health. 2021 Apr 8

Kimmel MC, Ferguson EH, Zerwas S, et al. Obstetric and gynecologic problems associated with eating disorders. Int J Eat Disord. 2016 Mar;49(3):260-75

Taneja S, Upadhyay RP, Chowdhury R, et al. Impact of nutritional interventions among lactating mothers on the growth of their infants in the first 6 months of life: a randomized controlled trial in Delhi, India. Am J Clin Nutr. 2021 Feb 10:nqaa383