Soft Drinks

Soft drink consumption is likely to influence obesity. Evidence suggests that people don’t compensate for the increase in energy consumed by drinking soft drink, and that soft drinks may provide insufficient satiety signals when compared with solid food .

In addition, soft drink consumption can stimulate appetite, as consuming high glycaemic carbohydrates can cause glucose levels to fall.

 Also, when processing soft drink the body may use less energy than when processing other food (lower thermogenesis).

The most recent national Australian data on soft drink consumption are presented by Gill, Rangan and Webb (2006). They found that about half of all teenagers and 36 per cent of 2–3 year olds had consumed soft drink in the past

24 hours.

Almost 60 per cent of males and almost 40 per cent of females in years 6, 8 and 10 drank more than 250ml of soft drink daily. In addition, between 7–12 per cent of males and a smaller proportion of females drank more than 1 litre of soft drink daily. It appears that male children consume more soft drink than female children , and soft drink consumption increases with age.

Between 1969 and 1999, soft drink consumption by adults and children more than doubled from an average of 47 litres per person per year to 113 litres per person per year (ABS 2000). A number of factors could explain this increase. First, increased availability of soft drinks, such as more vending machines, making it a relatively more convenient purchase. Second, a reduction in the relative price of soft drinks.

In the United States relative soft drink prices have decreased and consumption has increased over the past 20 years — soft drink consumption of 6–11 year olds roughly doubled between 1977–78 and 1998, and between 1982–1984 and 2000 the price of soft drinks increased by only 26 per cent, much lower than the overall consumer price index (80 per cent) and the price of fresh fruits and vegetables (158 per cent) (Sturm 2005).

A study conducted in regional Victoria (Sanigorski, Bell and Swinburn 2007) found that 4–12 year olds who consumed three or more servings of soft drink ‘yesterday’ were significantly more likely to be overweight/obese than those who consumed 0–2 servings.

A large international meta-analysis found a significant correlation between soft drink consumption and energy consumed.

However, the average size of the effect was small for children. Evidence for an association between soft drink consumption and body weight was mixed, and was influenced by how body weight was measured.

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Child Dietary intake

Dietary intake

Dietary intake contributes directly to energy consumed. Dietary intake in children may have changed over time, possibly contributing to the rise in childhood obesity.

A number of factors may have influenced the financial and time cost of food consumption, leading to a change over time.

First, agricultural and food processing innovation may have led to reductions in both the financial cost of food, and the time cost for preparing food.

Second, rising incomes increase the opportunity cost of the time spent preparing food. Third, increasing working hours also increases the time cost of preparing food.

The quantity of food consumed is not the only important consideration. The energy density of food is also important as different macronutrients (such as fat, protein and carbohydrates) contribute different amounts to energy intake. Also, fat, in particular, is stored more readily as fat in the body than other macronutrients (Davison and Birch 2001). Different macronutrients have different satiety effects that will promote or suppress additional dietary intake:

• Energy density influences the palatability of food, which will influence consumption.

• Different macronutrients have different thermic effects, which will influence energy expenditure.

• Energy storage in the body will be influenced by food composition and the metabolic efficiency of fat (Rodriguez and Moreno 2006).

Overall energy intake increased with age and the difference between males and females became wider as they got older. Just under half of total energy consumed came from carbohydrates for all age groups. Of this, sugars contributed more to energy intake in younger children, while starch contributed more to energy intake in older children. Dietary fat contributed just under a third to energy intake, with saturated fat contributing more than monounsaturated and polyunsaturated fat. Protein contributed about 17 per cent.

Cook, Rutishauser and Seelig (2001) found that 10–15 year olds in 1995 consumed significantly more energy than 10–15 years olds in 1985. In particular, they consumed significantly more protein, carbohydrates, starch, sugars, and dietary fibre. There was no significant change in intake of fat and cholesterol.

However, they were not related to BMI or triceps skinfolds. The authors concluded that macronutrient intake when young did not predict body fatness when older.

Another study, Sanigorski, Bell and Swinburn (2007), found significant positive relationships between daily servings of fruit juice/drinks and soft drinks and the probability of being overweight/obese. Surprisingly, children who consumed the highest amount of fruit and vegetables were also more likely to be overweight/obese than children who had consumed no fruit and vegetables the previous day.

This result could be due to a number of factors, including overweight/obese children eating a higher overall volume of food, overweight/obese children positively changing their diet in response to their weight, or reporting bias being stronger in parents of overweight/obese children. There were no significant relationships between the proportion of overweight and obese and daily consumption of fast foods and packaged snacks.

An international review (Newby 2007) found that, overall; there is no consistent association between childhood obesity and most dietary factors. The evidence on the relationship between total energy intake and obesity was the most inconsistent, but there was some evidence to support positive relationships between fat intake and consumption of sugar-sweetened drinks and obesity.

However, several methodological weaknesses in the studies covered by the review could at least partly explain the inconsistent findings, including interaction effects with other factors not taken into accounted, underreporting of dietary intake, genetic influences, different growth stages and generalisability of studies.

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