raditional diets are devoid of meaningful levels of refined carbohydrates, particularly sugar. However, changes to the composition of the typical human diet have occurred over the last 100 years in Western nations. The increasing intakes of sugar and other fructose containing molecules during this time, particularly in the form of sugar sweetened drinks, has been accompanied by a rise in the prevalence of Western lifestyle diseases. Recent studies are starting to show significant associations between sugar sweetened drink consumption and abdominal adiposity, insulin resistance, metabolic syndrome, obesity, type 2 diabetes and cardiovascular disease. High daily intakes of sugar and high fructose corn syrup containing soft drink increases the risk of obesity considerably because the fructose causes liver overload and increased de novo lipogenesis. These lipids are stored in muscle and hepatic tissues and are a primary cause of insulin resistance.
One study published in the International Journal of Obesity1 investigated the effects of changing four year intakes of various soft drinks and water in over 50,000 women aged 40 to 64. The results showed that increasing sugar sweetened soft drink consumption by 1 cup per day was associated with an increase in body weight of 0.36 kg. Over the same time period, increasing fruit juice by 1 cup per day was associated with an increased weight of 0.22 kg. However, water, tea, diet drinks and coffee were associated with a decrease in body weight of 0.13, 0.03, 0.10 and 0.14 kg, respectively. Both milk and whole milk were associated with increases in body weight of 0.02 kg over the same four years period. Substitution of sugar sweetened soft drinks or fruit juices by coffee, tea, water, diet drinks or milk was inversely associated with weight gain.
These results support other studies showing that sugar sweetened soft drinks are significantly associated with body weight gain. Fruit juices are often thought of as beneficial to the health because they are considered equivalent to fruit. However, fruit contains high concentrations of fibre, and this keeps the fibre to sugar ratio high in whole fruit. Because fruit juices lack fibre they are obesogenic in nature and contribute significantly to abdominal weight gain and insulin resistance. Tea and coffee have been reported on many occasions to favour weight loss, and this may be a result of the caffeine content. Sweetening both tea or coffee with sugar likely negates this effect and results in effects similar to those seen in sugar sweetened soft drinks and fruit juices. Although milk contains the sugar lactose, studies show that dairy products are inversely associated with weight gain and body weight, perhaps because of the calcium content.
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