Dr. Robert Lustig, MD, MSL

Lustig's research explains a pattern that blood sugar tracking alone misses. Fructose, the sugar in soda, fruit juice, and most processed sweeteners, barely raises blood sugar on its own. But it is processed largely by the liver, where it can be converted into fat, and Lustig argues it chronically suppresses leptin, the hormone that signals fullness. On his account, a food can look mild on a blood sugar monitor and still drive fat production in the liver and constant hunger through this separate pathway.

In Fat Chance he lays out this dual-mechanism argument: fructose drives fat creation in the liver and dampens the fullness signal, while insulin promotes holding on to fat. On that view, a food high in fructose and low in fiber can be a problem even when its immediate blood sugar impact looks moderate. RealFoods cites Lustig's published work on fructose and processed food as background for why blood sugar response alone does not tell the whole story. Lustig has not reviewed or endorsed the Weight Impact Score, which is RealFoods' own modelled estimate.

Metabolical widens the lens further, arguing that processed food, not personal willpower, is the primary driver of the modern rise in metabolic disease. That framing, examine what the food industry engineered rather than blame the person eating it, is central to the book. The RealFoods articles below cover related foods and topics.

Lustig's background in pediatric endocrinology adds another dimension to his argument. Caring for children with metabolic syndrome and early insulin resistance, he saw the same fructose-driven pattern showing up earlier in life than expected, tied closely to the rise of processed food and sweetened beverages in what children eat and drink. That clinical experience is part of why his work frames metabolic syndrome as a single connected condition, elevated insulin, liver fat, and leptin resistance moving together, rather than as a list of separate risk factors to manage individually. It is also why sugar science, in Lustig's work, is never just about blood sugar: fructose's near-total bypass of the normal blood sugar response is the kind of hidden mechanism he argues a blood sugar reading alone will miss.