Fat Deposition

The increase in maternal fat stores is by far the largest contributor to the energy cost of tissue deposition. It is also the most variable. Although the average increase for a well-nourished woman who has an uncomplicated pregnancy and healthy infant is approximately 3 kg, a large number of studies have reported ranges of —2 to 8 kg and standard deviations of 2-4 kg. There is also a wide range in fat deposition between different populations, particularly when those from developed and developing countries are compared. Fat is very energy dense and therefore changes in body fat stores have a large impact on the energy costs of pregnancy. A loss of 2 kg saves approximately 78 MJ (18 600 kcal), whilst a gain of 8 kg costs approximately 312 MJ (74 600 kcal). Women most likely to need an energy reserve to help meet the costs of lactation are often those who are least able to deposit spare energy as fat in pregnancy. Conversely, women who store large amounts of fat during pregnancy are least likely to need to use it during lactation. They are often able to increase food intake and/or decrease physical activity instead.

Table 3 Examples of current recommendations for energy intakes during pregnancy

Trimester(s)

Increment, MJ/day (kcal/day)

Total for pregnancy, MJ (kcal)

Qualifying comments

FAO/WHO/UNU

All

1.20 (300)

336 (80300)

(1985)

All

0.84 (200)

235 (56150)

For healthy women who reduce activity Energy and protein requirements are undergoing revision (interim report published 2004)

United Kingdom

3rd

0.80 (190)

74 (17 000)

Underweight women and

(1991)

those not reducing activity may need more

United States

1st

Adult EER + 0

For women aged 19-50 years

and Canada

(2002)

2nd

Adult EER +160 kcal (8 kcal/ week x 20 weeks) +180 kcal

EERs for pregnant adolescents are based on EER for 14- to 18-year-olds

3rd

Adult EER + 272 kcal (8 kcal/ week x 34 weeks) +180 kcal

EER is based on total energy expenditure in the nonpregnant state; increments for pregnancy are 8 kcal/week for total energy expenditure and 180 kcal/day for tissue deposition

EER, estimated energy requirement.

EER, estimated energy requirement.

Studies have shown that excess energy intake during pregnancy results in excess maternal weight (and fat) gain. Postpartum retention of excess fat has implications for the development of obesity and its comor-bidities such as type 2 diabetes.

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