In an important research study just published in the high impact American Journal of Clinical Nutrition, researchers have confirmed that switching from soft drinks in favour of diet drinks or water is an effective way to lose weight.
Sugar-laden soft drinks have been consistently linked to weight gain. Both the kilojoule content and also the fact that it comes in a liquid form which gives less of a feeling of fullness compared to solid food are likely reasons why drinking too much of them can result in weight gain.
A popular alternative to soft drinks are diet drinks. These beverages typically contain the artificial sweetener aspartame (trade names of NutraSweet or Equal). Aspartame is made by joining two naturally occurring amino acids (phenylalanine and aspartic acid) together which produces a substance that is 180 times sweeter than sugar.
So how effective is switching to diet drinks in helping control weight? If you were to take the evidence from observational studies only, it would paint a picture that people who consume diet drinks are more likely to be overweight. Unfortunately, such research cannot account for the very plausible reason that people who consume these drinks are trying to lose weight in the first place.
The best way to evaluate the effectiveness of diet drinks is by a randomised-controlled trial where people are randomly allocated to consume a diet drink or a full-sugar soft drink for a period of weeks to months. When such studies are done, the sum of evidence shows an average reduction of kilojoules consumed of around 10%, and a weight loss of 0.2 kg per week in those consuming diet drinks compared to those drinking regular soft drink.
Most of the research in this area though has been fairly short term of just a few weeks to months so it isn’t clear how effective diet drinks may be in the long term as a weight control strategy.
Diet drinks help with weight loss
The new research study used a much larger number of people (318 overweight and obese adults in total) and ran for 6 months. Each person was randomly allocated to one of three different groups: switch to diet drinks, have just plain old water instead, or serve as the control group. People in the control group were counselled on healthy eating and exercise habits, but were not specifically advised to make a change to their beverage consumption habits.
People drinking the diet drinks lost 2.5% of their body weight by 6 months. This compared very favourably to those who were allocated to water in place of soft drink who lost 2% of their body weight, and 1.8% of body weight lost in the control group. People who were assigned to diet drinks or water were twice as likely as those in the control group to have achieved a weight loss of 5% or more after 6 months.
And before you get too carried away and raise alarm about drinking ‘cancer-causing artificial sweeteners’, you may wish to read this credible evidence-based commentary on the matter first rather than believe anonymous scaremongering chain emails.
What it all means
Making positive dietary changes by cutting back on soft drink and replacing it with a similar tasting diet beverage or even water is a small, but effective way in helping with weight loss.