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What they found was that restricting soda intake over a period of 10 weeks to 8 months led to a 0.8 kg (1.75 lbs) weight loss. Increasing soda intake had the opposite effect, leading to a .75 kg (1.65 lbs) weight gain. The biggest weight gains were in those who'd increased intake the longest (longer than 8 weeks), where gains were a substantial 2.73 kg (6 lbs). But even over the short term (less than 8 weeks), soda was linked to a .5 kg (1.1 lbs) increase.
The findings for kids were less solid than those for adults, but the analysis still found a link between soda intake and weight. Kids who drank the most soda were found to have a 50 percent higher risk of being overweight than kids who drank the least soda.
While this link between soda and weight may not seem groundbreaking - nor the amount of gains and losses - this paper provides solid data that have been lacking and should give a boost to efforts to curb sugary soda consumption.
One way sugary sodas can lead to weight gain is simply by adding to the total of daily calories. The calories in sodas aren't as filling as those in solid foods, so even though sodas add significant calories to the daily diet, they do so in a stealthy manner, little noticed by the body. So it's easy to not compensate for them by cutting back elsewhere. Sugary soda can also cause spikes in blood glucose level, which then cause spikes in blood insulin levels as a way to bring glucose back down. This big drop in glucose, though, can bring on feelings of false hunger, leading to extra eating and calories.
This spiking and crashing of glucose and insulin is also one mechanism through which sugary drinks (and sugary foods) can raise the risk of heart disease and diabetes. And the weight gain linked to soda consumption can raise the risk of a number of chronic diseases, including stroke, diabetes, heart disease, and many cancers.
In an accompanying editorial, Walter Willett and David Ludwig note that efforts to restrict soda consumption are very import - and are showing some promise - but should also be part of a larger effort to improve the overall quality of carbohydrates people consume. Starchy foods like potatoes and highly refined grains can boost blood sugar levels just as forcefully as sugary drinks.
Important steps to improving the quality of carbohydrates include:
- Limiting sugary drinks, including soda, energy drinks, and fruit punch
- Choosing whole grains products more often, like brown rice, 100% whole wheat bread, popcorn (little salt, no butter) and whole oats
- Limiting refined grains, like white rice, white bread, and pasta
- Eating a lot of whole fruits and vegetables (except potatoes)