Nutrition during pregnancy
Energy restriction and nutrition during pregnancy
Severe energy restriction to lose weight is not appropriate nutrition during pregnancy. It is unlikely to be beneficial and may harm the foetus. Inadequate energy and nutritional intake, particularly in the first trimester, is associated with an increased incidence of low birthweight infants, with associated impacts on later health (see section 2.3.1) and congenital abnormalities, such as neural tube defects (Carmichael et al 2003). Excessive weight loss in pregnancy can produce ketone bodies and other metabolites that can create metabolic stress and may be detrimental to foetal development. Maternal health may also be compromised, and breast growth and development in preparation for breastfeeding may be affected.
Historically, there were two reasons for recommendations to restrict energy and protein intakes in pregnant women: the risk of developing pre-eclampsia and to prevent obesity. However, energy and/or protein restriction has no effect on the development of pre- eclampsia, and excessive weight gain is the result, not the cause, of the underlying clinical pathology. In obese women, severe energy restriction is associated with a reduction of mean birthweight (Merialdi et al 2003), although some moderate reduction of energy intake to control weight gain may be appropriate.
2. Return to pre-pregnancy weight
Breastfeeding is associated with post-partum weight loss, but weight loss is highly variable (Butte et al 2003). It has been suggested that periods of breastfeeding longer than six months are required to ensure significant weight loss (Kac et al 2004).
The pattern and timing of weight loss during breastfeeding vary. The pattern of body fat loss generally reverses the pattern of weight gain during pregnancy, with loss of subcutaneous fat and fat from the hips and thighs (Butte and Hopkinson 1998). The rate of weight loss among well-nourished women may be primarily associated with a desire to lose weight and be the result of an intentional reduction of dietary energy intake (Rogers et al 1997). Although the additional energy requirement of breastfeeding leads people to expect a greater rate of weight loss among breastfeeding women, this does not always appear to be the case (Chou et al 1999; Wosje and Kalkwarf 2004). Most women lose weight gradually while breastfeeding, some women actually gain weight, and others lose weight relatively rapidly. Women need to allow adequate time to readjust after pregnancy, and weight loss after delivery should not be expected to occur before 9–12 months. There is a lack of information on rates of weight loss while breastfeeding after the first 12 months post-partum among well- nourished women.
Post-partum weight and fat retention are significantly correlated to GWG, specifically gestational fat mass gain (Butte et al 2003). Women with high post-partum weight are more likely to have gained excessive weight during the first 20 weeks of pregnancy (Brown et al 2002). Controlled studies in well-nourished women living in developed countries suggest that, on average, women increase body weight between conception and one year post-partum by 0.5–3.3 kg (Ellison and Harris 2000). Variations in post-partum weight retention suggest that it is not solely attributable to the effects of pregnancy (and/or the immediate post-partum period). Increased body weight is associated with age, increased parity, socioeconomic and
3. Food and Nutrition Guidelines for Healthy Pregnant and Breastfeeding Women: A background paper
Marital status, increased intake, decreased activity, and other factors such as psychosocial stress, isolation and loneliness, which may become apparent in the post-partum period.
There are difficulties in accurately assessing the extent of weight retention following pregnancy. Body composition can change from very early in the first trimester and many women do not return to their pre-pregnancy weight, so it is difficult to determine a reliable baseline BMI measurement (Kopp-Hoolihan et al 1999). The difficulties are compounded by women self-reporting pre-pregnancy weights that have a skewed distribution, suggesting they report a desired rather than an actual pre-pregnancy weight.
Physical activity alone, without intentional moderate reduction in energy intake, does not seem to lead to weight loss, because exercising women tend to have higher dietary energy intakes than their sedentary counterparts (Lovelady et al 1990; Dewey 1998). Breastfeeding women may accelerate weight loss by reducing energy intake and increasing physical activity. A weight loss of 0.5 kg per week in overweight breastfeeding women, achieved by moderate reduction in energy intake and increase in physical activity, does not appear to affect milk production (Lovelady et al 2000), although researchers have not assessed more subtle indicators, such as infant satisfaction (Lovelady et al 1990). If physical activity is included along with moderate reduction in energy intake, most of the weight lost will be body fat (McCrory et al 1999). Loss of body fat associated with breastfeeding may be more likely after 12 weeks post-partum (McCrory et al 1999; Lovelady et al 2000).
High-protein, low-carbohydrate diets are not recommended while breastfeeding and during pregnancy. It will be difficult to achieve adequate intakes of micronutrients, and to meet the requirement for glucose for lactose synthesis, lactose being the primary sugar in breast milk. Although the body can produce some glucose itself, it is not clear that sufficient quantities can be produced to support a high rate of milk synthesis, with a possible result of reduced milk supply. The flavour and odour of breast milk may also be affected by the presence of ketone bodies (Heinig and Doberne 2004), which may be produced as a result of a high- protein, low-carbohydrate diet.
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