Mechanisms on childhood overweight and obesity at high altitude

Abstract

Abstract

Objectives:

The present study with its three parts, was undertaken to: (a) Describe the body composition and

determine the prevalence of overweight and obesity in high altitude children’s population and

compare them their counterparts at low altitude, (b) Determine the possible mechanisms by

which high altitude influences childhood body composition and the prevalence of overweight

and obesity, (c) Explore the possible role of administration of antioxidants during pregnancy at

high altitude in preventing late childhood overweight and obesity.

Materials and methods:

The first part was a cross-sectional prospective study of 145 Saudi children born and living

permanently at high altitude (3100m) and 154 Saudi children born and living permanently at

relatively low altitude (500m). For each child selected information regarding birth weight and

breast feeding were taken from his or her file. Anthropometric measurements were then

performed. Body mass index was calculated using the equation BMI=(Weight (kg)/Height (m2

).

Fat mass and fat free mass percentages were derived from triceps skinfold measurement. Resting

pulse rate (beats/min), blood pressure, haemoglobin concentration and haematocrit value were

measured. Physical activity level was determined using the short form of international physical

activity questionnaire (IPAQ-SF).

The second part was also a cross-sectional prospective study which included 25 healthy pregnant

women and their healthy newborns from high altitude and equal numbers from low altitude.

Measurements of maternal haemoglobin concentration, haematocrit value and blood pressure

were made at the end of gestation. Foetal haemoglobin concentration and haematocrit value were

2

determined immediately after delivery. Determination of the newborn's body shape and body

composition were made from anthropometric measurements. Placental weight was determined

immediately after its delivery. Placentae were then examined histologically.

The third part was performed on pregnant Wistar rats which were distributed

into three groups: Vitamin E treated group (injected intraperitoneally with

vitamin E) on alternating days throughout pregnancy, vehicle treated group

(injected intraperitoneally with olive oil) also on alternating days throughout

pregnancy and control group (receive nothing). For each rat in the three

groups haemoglobin concentration and haematocrit value were measured.

After sacrification of each rat in the three groups number of pups and birth

weight were determined. Haemoglobin concentration and haematocrit value

were measured. Placental oxidants and antioxidants were measured in

placental tissues. Placentae were then examined histologically.

Results: The percentage of fat and the overall prevalence of overweight and obesity among

children aged 10-15 years were significantly greater among highlanders than among lowlanders

(P<0.01 and < 0.004 respectively), while the percentage of fat free mass showed an opposite

trend (P<0.01). The average birth weight of highland children was found to be significantly

greater than their respectives at lowland (P<0.01). Highland children reported lower level of

physical activity than lowland ones. Birth weight was found to be positively and significantly

associated with the percentage of fat free mass and negatively and significantly with the

percentage of fat mass and the prevalence of overweight and obesity. Physical activity level was

found to be inversely and significantly related to overweight and obesity in boys at both altitudes

but there was no clear trend for girls at either altitude.

3

Compared with their respectives from lowland, highland pregnant women and their placentae

showed haematological and histological changes suggestive of maternal and placental hypoxia

respectively. There was no haematological evidence suggesting that the high altitude foetuses

experienced a greater degree of hypoxia in utero than did the low altitude foetuses. Compared

with lowland newborns, highland newborns were significantly lighter, fatter and had greater head

circumference: birth weight ratio and abdominal circumference and significantly lesser chest and

lower limbs circumferences and fat free mass. These differences in body physique between high

and lowland newborns appeared to be mainly secondary to placental hypoxia resulting from

maternal hypoxia which in turn was caused by high altitude hypoxia.

Administration of Vitamin E to pregnant rats at high altitude reduced maternal hypoxia which

resulted in a decrease in placental oxidative stress and placental hypoxia leading to significant

increase in the number of newly born pups and insignificant increase in the total and individual

birth weights of the newborn pups.

Conclusion: Highland children of Southwestern Saudi Arabia were found to be significantly

fatter, significantly less leaner and have significantly higher prevalence of overweight and

obesity when compared with their respectives at lowland. These differences in body physique

were attributed to the low birth weight, caused by placental hypoxia, and low physical activity

level among highland children compared to lowland children. Administration of vitamin E to

pregnant rats at high altitude decreased maternal and placental hypoxia and ultimately caused

significant increase in the number of newborn pups and insignificant increase in the total and

individual birth weight of newborn pups. These results call for controlled trial study to

investigate the effect of vitamin E on birth weight in pregnant women at high altitude.

4

Meanwhile pregnant women at high altitude are advised to take diet rich in vitamin E throughout

pregnancy to improve birth weight and thereby reduce late childhood overweight and obesity.

Also physical activity should be encouraged as strategy directed towards weight reduction in

overweight and obese children as well as prevention of overweight and obesity in Saudi high and

lowland children.