If You Want to Lose Weight and Stave it Off, You'd Better Not Drink Water Instead of Artificially Sweetened Beverages

Meanwhile, even many of those who are against the use of sweeteners admit that drinking diet coke is less of an obstacle to weight loss than regular coke. That it could, as the study at hand clearly indicates, even promote weight loss compared to water is controversial, though.

It is one of the die-hard rumors in the fitness industry: Artificial sweeteners will stall your weight / fat loss and have your weight jojo back up, when you stop dieting. As a SuppVersity reader you know that this claim is not supported by science. For the first part, controlled trials like the 2014 study by Sørensen et al. actually show that the exact opposite is the case, i.e. that the consumption of artificially sweetened beverages promotes, not hinders weight loss.
To be more precise, Peters' study was a year-long trial designed to compare the effects of beverages sweetened with non-nutritive sweeteners (NNS) to water as part of a behavioral weight management program consisting of 12 weeks of active weight loss (results previously published in Peters et al. 2014) and 40 weeks of weight maintenance (results now published in Peters, et al. 2016).

Figure 1: Weight and waist loss during the initial 12-week weight loss phase of the study (Peters. 2014).

As previously discussed in the SuppVersity News on Facebook, the results from the 12-week weight
loss phase of this trial were in line with those of the previously cited study by Sørensen et al. (2014) - with the important difference, however, that Sørensen et al. compared non-nutritive sweeteners (NNS) to sugar-sweetened beverages, while Peters et al. found that the NNS group experienced greater weight loss during the 12 weeks of active weight loss, as well as more pronounced reductions in waist circumference, blood pressure, cholesterol, LDL, and triglycerides, even if the control group consumed plain water group (Peters. 2014 | see Figure 1 for weight and waist data).

Figure 2: Consuming NNSs decreased the hunger of the subjects during the 12-week weight loss phase (Peters. 2014).

Mechanistically, the observed benefits may be explained by the opposing effects the consumption of NNS sweetened beverages and water had on the subjects' appetite: Unlike the group that kept consuming artificially sweetened beverages and experienced a significant reduction in hunger scores even while dieting, the ones who were allowed to consume only water reported significantly increased levels of hunger on the 0-100 pts hunger scale Peters et al. used (see Figure 2).
In the follow up paper, Peters et al. (2015) now report that the 158 male and female subjects in the NNS group did also have an easier time maintaining their weight loss than their 150 peers in the water only group (see Figure 3); a result of which the scientists say that it was neither due to differences in physical activity / sedentary time or caffeine intake, which were (within the usual statistical margins) identical in both groups.

Figure 3: Body weight (in kg) after 52-week (weight maintenance phase | left) and percent body weight regained during the weight maintenance phase (grey = water; black = NNS | right; Peters. 2015).

While Peters et al. (2015) rightly point out that "it is not possible from the present data to explain why the NNS group lost more weight than the water group despite receiving identical weight loss instruction and beverage interventions that both contained zero calories", they are right to conclude that their findings ...

"[...] are important as there continues to be uncertainty about the benefit of NNS for weight management based largely on observational studies showing associations between NNS consumption, obesity and weight gain." (Peters. 2015).

This is particularly true in view of the fact that the data clearly opposes the often voiced claim that NNS promote obesity by interfering with normal mechanisms of energy balance.
This claim, however, is - as far as experimental evidence is concerned - based exclusively on animal studies; studies that conflict with both, the study at hand and the few other published long-term human trials that evaluated NNS for weight loss (Blackburn. 1997; Tate. 2012):