Obesity

Defined by a body mass index of 30 or above, obesity affects 42.4 percent of US adults according to 2023 CDC figures and some 650 million adults worldwide, a prevalence that has tripled since 1975. The condition is polygenic, with more than 200 implicated genes, and it interacts with sleep, chronic stress, medication, the food environment, and the composition of the gut microbiome. Eleven ingredients are graded against it here, a larger set than for any other condition on this site, drawing on 116 studies and about 7,800 participants; the grades run from A to D, and two entries record a mixed rather than a positive direction of effect.

Glucomannan holds the Grade A position on 9 studies and 509 participants, by the same soluble-fiber mechanism that supports its appetite grading. Four ingredients occupy Grade B: conjugated linoleic acid on 18 studies and 807 participants, green tea extract standardized for EGCG on 14 studies and 1,500 participants, alpha-lipoic acid on 12 studies and 534 participants, and vitamin D on 11 studies and 947 participants. Vitamin D is the conceptual outlier, since low status is common in obesity and the causal direction between the two remains contested.

The Grade C tier is where most of the commercially prominent products sit. Probiotic Lactobacillus gasseri and prebiotic inulin each carry 15 studies, with 1,500 and 800 participants respectively; both act on the gut microbiome, a target whose relevance to functional-food research was already being argued two decades ago ^[1] and whose fermentable substrates, the dietary fructans, have an equally long descriptive literature ^[2]. Garcinia cambogia also sits at Grade C, on 12 studies and 800 participants, but with a mixed direction of effect: the trials do not agree with one another. Glutamine on 7 studies and forskolin on 3 studies and 80 participants complete the tier on notably thin bases.

Raspberry ketones occupy Grade D, and the record is explicit about the reason: zero studies and zero participants in the human clinical literature assembled here, alongside a mixed direction of effect. Commercial visibility and evidentiary support are independent variables, and this entry is the clearest illustration of that independence in the set.

Two caveats govern the table as a whole. Supplement trials in obesity are generally short, commonly 8 to 24 weeks, while the condition is lifelong, so persistence of any observed effect is rarely established. And the mean differences reported are small relative to the clinical thresholds that matter, which is why none of these ingredients is positioned as a substitute for the dietary, behavioral, pharmacological, and surgical options a clinician weighs. Sleep apnea, joint pain, breathlessness on exertion, and raised inflammatory markers commonly accompany the condition and warrant medical assessment independently of any supplement decision.