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<0.001). Increased GWG was associated with increased self-reported total energy intake in lean, but this was not seen in obese. GWG was not associated with PA in either group. BWT was not significantly different between obese and lean (3,547±549g vs 3,567±516g). In lean, increased BWT was associated with increased energy intake and total PA. BWT in obese was not associated with diet but with increased with PA in early pregnancy. In conclusion, self-reported methods were less reliable in assessment of diet and PA in severely obese compared to lean pregnant women. These exploratory studies found that obese women did not appear to have the same factors as lean women affecting GWG and BWT, though this may be complicated by the poor reliability of self-reports. Therefore, quantitative assessments such as measurement of serum micronutrient levels (to evaluate nutritional status), and accelerometry (to assess physical activity) may be necessary in this poorly understood population.

Introduction: Obesity has become a major world-wide health issue. Social-economic status, physical activity levels and dietary intake may influence the weight status in children. However, these issues have not been examined together in studies of young girls in Saudi Arabia. Aim: This study aimed to investigate energy and nutrient intakes, physical activity and social economic status of girls aged 8-11 years in western Saudi Arabia according to their BMI. Methods: This study was conducted in two phases, phase one was a pilot study where 32 girls were selected to assess the suitability of body composition, dietary intake (food diary, food frequency questionnaire) and physical activity measurement tools (pedometer, physical activity questionnaire). The findings of this phase were employed in phase 2; the diet diary and accelerometer were nominated as assessment tools. In phase two, girls (n= 234) participated from different schools. Waist circumference, height and weight were measured and BMI was calculated. Girls were classified according to BMI centile charts (CDC). Dietary intake was measured via a 4-day food diary and accelerometers were used to assess the intensity and time spent in physical activity. Results: A total of 30% of the sample were classified obese or overweight. There was a significant difference in the mean daily energy intake between the BMI groups with the obese group having the highest energy, fat, carbohydrate and protein intake (obese group: 2677 ± 804 kcal/d; healthy weight group: 1806 ± 403 kcal/d, p< 0.001), but the percentage contribution of the macronutrients to energy intake remained the same across the BMI groups. Carbohydrate intake was shown to be the main contributor to predict obesity levels. VI There were no differences in number of steps taken per day or time spent in moderate/ vigorous intensity exercise according to BMI category. Most of the girls did not meet daily physical activity guidelines (5969 to 6773 steps per day and 18.5 - 22.5 mins per day of moderate- vigorous activity). Intake of sweets and sugary drinks, and total energy intake were significantly higher in the high income group compared to the low income group. However, family income was not associated with BMI status. Conclusion: The results of this study suggest that obesity in girls aged 8-11 years is linked to excessive energy intake from all macronutrients and the majority of girls in all weight categories are inactive. Research should be conducted to develop interventions to promote dietary change and activity that is culturally acceptable for girls in Saudi Arabia.

Background: Data on objectively measured physical activity (PA) in preschoolers are controversial. Direct accelerometry was performed in children aged 3–6 years, and differences in PA patterns over the course of the week were evaluated. Data were analyzed with gender, BMI, lifestyle, and socioeconomic parameters as covariates. Methods: PA was measured in 119 children by the SensewearPro accelerometer and analyzed in the 92 (40 girls) that wore it for at least 4 days including one day of the weekend. Median measuring time in this group was 7 consecutive days (median/mean daily measuring time: 23.5 h/d and 21.8 h/d, respectively), corresponding to 834,000 analyzed minutes. PA questionnaires were completed by 103 parents and 87 preschool teachers to collect anthropometric, lifestyle, and socioeconomic data. Results: Median daily PA (MET.3) was 4.3 hours (mean: 4.4 hours). Boys spent an estimated 52 min/week more being very active (MET.6) than girls (95% CI [6, 96] min/week, p = 0.02). PA was lower during the weekend (3.7 h/d) compared to weekdays (4.5 h/d), p = 361026), where a 95% CI for the difference is [0.5, 1.0] h/d. PA levels did not differ between overweight/obese children (median 4.7 h/d) and normal-weight peers (median 4.2 h/d). Daily media consumption increased with decreasing social class on weekdays (p = 0.05) and during the weekend (p = 0.01), but was not related to the amount of daily PA. A multivariate regression with BMI-SDS as independent variable and gender, age, amount of PA.6 MET, parental BMI, media time and socioeconomic status as explanatory variables revealed that only SES had a significant contribution. Conclusion: The negative impact of obesity-promoting factors in older children is rather low for preschoolers, but there is evidently a gradient in PA between weekdays and weekends already in this age group. Weight status of preschoolers is already considerably influenced by SES, but not physical activity levels.