Dietary intake and physical activity in severely obese pregnancy in Scotland

Maternal obesity is associated with adverse effects for mothers and offspring. The primary aim of this thesis was to assess food intake and physical activity (PA) using validated self-administered questionnaires, and whether these were associated with gestational weight gain (GWG) and birthweight (BWT), in severely obese (body mass index, BMI≥40kg/m2) compared with lean pregnant women (BMI 20-25kg/m2). The secondary aims were to validate self-reports against food diary (FD) and accelerometry; to assess the prevalence of under or over-reporting of energy intake; and to carry out a pilot study to assess total energy expenditure, as well as self-reporting accuracy, by using doubly-labelled water (DLW) technique, in subgroups of participants. Pregnant women were recruited from an ongoing study of severe obesity in pregnancy at the Royal Infirmary of Edinburgh, UK. Assessments were done in early (12-20 weeks) and late (28-32 weeks) pregnancy. A subgroup of women also completed questionnaires on appetite, general nutrition knowledge, and eating behaviours. All results were adjusted for age, parity, ethnic origin and deprivation category score. Self-reported total energy intake was not significantly different between obese and lean during early (median 2,444 vs 2,312 kcal/day) and late (2,173 vs 2,354 kcal/day) pregnancy. However when validated with FD, the relative validity of the food frequency questionnaire was lower in obese compared to lean. Under-reporting of total energy intake was higher in obese compared to lean (49% vs 15%, P<0.01) through comparison of selfreported energy intake with estimated total energy expenditure, and this was supported by the DLW pilot study results. The DLW also showed possible over-reporting of PA by the obese group. Obese women reported significantly lower appetite than lean throughout pregnancy (P<0.01). They also had lower scores in general nutrition knowledge, but these were no longer significant after controlling for confounders. Obese women had significantly higher scores of restrained and emotional eating behaviours than, and similar scores of external eating behaviours to, lean. Appetite, nutrition knowledge, restraint and emotional eating behaviours scores were not associated with food intake in either obese or lean. On the other hand, increased intakes of total calories and fats were influenced by increasing score of external eating behaviour in both groups. Obese women reported doing similar amounts of total PA but significantly less of vigorous and sports and exercise activities than lean (P<0.05). Accelerometry showed obese women had lower average activity counts/day, although they did have significantly greater energy expenditure in light-intensity activity than lean (P<0.01). Obese women had less GWG than lean (Mean ± SD, 5.3± 52 vs 10.8±3.7kg, P