NOTES: REVIEW OF THE LITERATURE

1. Factors and researchers’ findings.

Critical periods
Dietz, professor of pediatrics, points out 3 critical periods that relate to the obesity development in childhood. They are ″gestation and early infancy″, ″the period of adiposity rebound that occurs between 5 and 7 years of age″, and ″adolescence″. Indeed, she relates the first period to early adiposity in adulthood, the second period, the adiposity rebound, to early maturation, and the last period to greater obesity in adulthood. While Deckelbaum et al. state that the worst time to be overweight or obese is during adolescence not only due to prevalence of obesity during adulthood but even if surplus of weight is lost as adult, high risk of mortality remains. Deckelbaum also argues that urgent research are needed in the field of prevention and treatment of obesity in childhood. Dietz also adds that when obesity develops during these 3 critical periods, ″the risks of persistent obesity″ during span-life is higher than those who do not develop these factors at a young age. Jefferey (2004, 821) agrees that early development of fatness is a risk factor.


Genetics

Dietz (1994) underlines that genetics is one factor associated with familial obesity. Dietz (1994) However, she mentions that ″nutritional alterations at critical periods″ have not been yet researched. Seeley (2005, 16) attests that the family history is an important factor which indicates that children who have 2 obese parents will probably be overweight during their youth. She adds that although many studies have been made about the genetic factor, the results are still not conclusive and Statistics Canada agree with this statement but add that it has to be researched together with environments, behaviour, and lifestyle factors. While Jeffery (821) strongly declares that gene factor is the most striking factor that contributes to obesity: not the environment. This would account up to 50% of obesity. Torgan (2002) argues that adolescents suffering from overweight have great risk to become obese adults. She affirms undoubtedly that genetics is a factor but that genes are not the only responsible to fatness. Kiess, Marcus, and Wabitsch (2004, 80) ″forsee that obesity will be viewed as a more genetically determined condition than is currently the case″. Indeed, he adds that "50% of the tendency towards obesity is inherited". Finally, they. range the genetic factor contribution to fatness between 25 and 40% (117). Mela et al. (1998, 62-63) suggests strongly that genetics is the most important factor and supports its comments saying that the environment would count only for a small percentage of factors in adulthood.


Nutritional

Dietz (1994) declares that over-nutrition or under-nutrition during prenatal period plays a role in overweight at a later time and that many studies show that birth weight is related to later obesity. However, in Seeley (2005, 14, 20, 21) review of the literature, she indicates that studies are still controversial since research do not all agree with the fact that breast feeding always lead to lean children and that this aspect is complex. However, she supports that a high saturated fat intake is a strong factor which many studies agree with. Jeffery (2004, 821) points out that research is missing about the relationship between fat intake and total energy intake (but prefer saying fat intake instead of energy intake) and add that fat intake is more risky for developing fatness. Torgan ( )also agrees that too much calories intake and too little physical activities are main factors. Statistics Canada (2006) highlights that the calorie intake should be measured according to age, sex, weight, height and activity level. They also note that the Canadians’ calories intake has not increased in 2004 compared with the survey made in 1970-72. Kiess, Marcus, and Wabitsch (2004, 80) extrapolates that "over consumption of fat-rich diets" and too little physical activities due to watching television and playing video games "heavily contribute" to gaining surplus of weight and conclude that more research is needed to measure excess energy intake versus energy expenditure (viii). Părízková (2005, 7) says that the diet composition "with high intake of fat and/or sugar" has been studied. She also advances that “many studies have not shown any significant differences between the food intake of obese and normal-weight subjects". Kiess, Marcus, and Wabitsch (103-5) agree with Jeffery statement (821) that relationship of energy intake between normal and overweight children is difficult to control due to underreported intake energy from non normal weight children. But they advance that a fat dietary intake is a great aspect of fat increasing. They report that more frequent daily meals help reducing the risk of gaining. On the other hand, they report that "Most people believe that obese and overweight children have a higher energy and fat intake than normal-weight children. However, no clear-cut associations were found in nutrient and/or food intake and bodyweight. "


Prevention and environment

Jeffery (819) indicates that research showed that to lose weight, the environment has to be changed. However, prevention remains the secret to stay lean and adds that ″obesity is not innate, but rather develops over time″ The prevention aspect has not yet been studied. He also highlights that obesity is difficult to treat. Even if Mela et al. (1998, 62-63) think that genetics is the major factor, they lessen its importance saying that prevention diet in childhood may control later obesity.


Socioeconomical

Seeley (2005, 14, 18) states that the socioeconomic factor has been studied and showed that when parents have a low level of education and are low-income, children overweight could be associated to these factors but that more studies are needed since this factor is complex. Statistics Canada tends to reflect Seeley statements with the study made in 1998/99. They found that due to low income (and middle-income), people changed their usual food intake because they were afraid to not have enough money. This is what they call ″food insecurity″. They also showed that 29% of children below 18 already lived a situation of not having the necessary food. Most of low-income family children do not suffer from under-nutrition because parents sacrify themselves instead. They add that ″during infancy and childhood, a poor nutrition diet is related to many development problems but do not discuss about later obesity problems. They conclude that children need more calories and nutrients than adults.


Physical activity

According to Seeley (2005, 14; 19), all studies seem to correlate that the more a child is active, the less fat amount he has but confirms that more research is needed since it is a complex factor. Jeffery (2004, 821) claims that not enough exercise is one of the factors and reports that the obese are less active than those who are not. The research made by Statistics Canada in 1994/95 shows that many factors are related to physical activity. Indeed, they narrate that ″people who are young, well-educated, healthy, former smokers, or had a high sense of mastery tended to begin or continue to be physically active″. But their study relies on adults from 20 to 65 years of age. Kiess, Marcus, and Wabitsch (105) noticed that even if overweight children do not change their high fat diet intake, they can lose some percentages of adiposity by doing physical training.


Statistics Canada. Overweight and Obesity Among children and Youth.
"In 2004, 26% of Canadian children and adolescent from 2 to 17 were overweight or obese and 8% obese.″

Health Canada. "Canadian Guide food" (see my arguments)


U.S. Food and Drug Administration. How to understand the Nutrition Facts Label. (see my arguments)


Encyclopedia Britannica, consulted jan. 22, 2007.

They give the definition of obesity and explain the suffering expectations of obese people. The article is broad. It does not discuss any research. So, I will not use it in my research.