Hypotheses and evidence related to intense sweeteners and effects on appetite and body weight changes: A scoping review of reviews

Abstract

Observed associations between consumption of diet foods and obesity have sparked controversy over whether intense sweeteners may promote weight gain, despite their negligible energy contribution. We conducted a scoping review of reviews, to obtain an overview of hypotheses, research approaches and features of the evidence on intense sweeteners' potential relationships to appetite and weight changes. We searched for reviews of the scientific literature published from 2006 to May 2017. Two reviewers independently assessed title and abstracts, and full text publications. Arksey and O'Malley's framework for scoping reviews guided the process. We extracted and charted data on characteristics of the reviews and the evidence presented. The 40 included reviews present hypotheses both on how intense sweeteners can reduce or maintain body weight and on how these can promote weight gain. We classified only five publications as systematic reviews; another nine presented some systematic approaches, while 26 reviews did not describe criteria for selecting or assessing the primary studies. Evidence was often presented for intense sweeteners as a group or unspecified, and against several comparators (e.g. sugar, water, placebo, intake levels) with limited discussion on the interpretation of different combinations. Apart from the observational studies, the presented primary evidence in humans is dominated by small studies with short follow-up-considered insufficient to assess weight change. Systematic reviews of animal studies are lacking in this topic area. The systematic evidence only partly explore forwarded hypotheses found in the literature. Primary studies in humans seem to be available for systematic exploration of some hypotheses, but long-term experimental studies in humans appear sparse. With few exceptions, the reviews on intense sweeteners and weight change underuse systematic methodology, and thus, the available evidence. Further studies and systematic reviews should be explicit about the hypothesis explored and elucidate possible underlying mechanisms.

Fig 1. Literature search and selection process.

Fig 2. Features of included reviews without description of study selection, all narrative analyses.

Fig 3. Main hypotheses identified from all included reviews mapped against the evidence found in systematic reviews and reviews with systematic approach to study selection.

^a Data extracted from systematic reviews and reviews with description of systematic approach (from Table 1). Categorisation is based on our judgement of the aim, research question or hypotheses presented, study inclusion criteria and analyses presented in each review against the hypothesis. Evidence summaries of observational studies were not considered for this presentation. A: Animal studies.

Fig 4. Number of participants and longest follow-up time^a in cited observational studies (n = 24).

Data from the reviews in Table 1 that presented characteristics on all included primary studies. All studies presented results on diet soda consumption with unspecified type of intense sweetener used. ^a For studies analysed in multiple primary publications, the longest follow-up is presented.

Fig 5. Number of participants and longest follow-up time in cited human experimental studies (n = 118) in categories defined by intense sweeteners versus comparator studied.

Data from the reviews in Table 1 that presented characteristics on all included primary studies. ^a One study with 641 participants and 78 weeks follow-up outside chart area. ^b One study with 414 participants and 43 weeks follow-up outside chart area.