Real cellular biology, and a marketing leap well beyond what the lab research supports.
The Sirtfood diet gained fame as "the diet Adele reportedly used," built around foods believed to activate sirtuins — proteins involved in cellular regulation, sometimes nicknamed "skinny genes" in marketing material for the diet.
Sirtuins are indeed real, genuinely interesting proteins studied in aging and metabolic research — resveratrol (found in red wine and grapes) was an early compound of interest for activating them. The foods on the Sirtfood list (kale, red wine, dark chocolate, berries, coffee) do contain polyphenols that have been studied for various health benefits.
The specific claim that eating these foods meaningfully activates sirtuins in a way that drives significant fat loss in humans is a considerably bigger leap than the underlying lab research supports — most sirtuin research involves animal models, isolated cells, or concentrated compound doses far beyond what a normal serving of kale or red wine provides.
The foods themselves (kale, berries, dark chocolate in moderation) are perfectly reasonable additions to any diet — just hold the "activates your skinny gene" framing loosely.