Abstract

  Obesity with type 2 diabetes (“diabesity”) arises when chronic caloric excess, low diet quality, and circadian 
misalignment overwhelm metabolic flexibility. Nutrition is therefore both cause and cure. Evidence across 
mechanistic studies and randomized trials shows that energy deficit can be achieved via continuous caloric 
restriction (CR), intermittent fasting (IF), or time-restricted eating (TRE), which improves glycemia, hepatic 
steatosis, and insulin sensitivity primarily by shrinking adipocyte size, reducing ectopic fat, and decompressing 
mitochondrial/ER stress. Beyond calories, macronutrient patterning matters: low-carbohydrate and 
Mediterranean-style diets often yield superior short-term glycemic control; high-quality low-fat patterns can 
be equally effective when adherence is high. Carbohydrate quality, like fiber, resistant starch, glycemic 
index/load, and food processing, modulates postprandial glucose and the gut–liver axis. Meal timing and 
circadian alignment shape insulin action and β-cell responsiveness independent of weight. Bioactive-rich foods 
and microbiome-directed strategies add complementary effects via short-chain fatty acids, bile-acid signaling, 
and inflammation control. The clinical frontier is precision nutrition: using continuous glucose monitoring 
(CGM), phenotyping (adiposity distribution, NAFLD, fasting/postprandial hyperglycemia), and, where 
validated, microbiome/metabolite readouts to tailor diet choice, meal timing, and macronutrient distribution to 
the individual. Implementation hinges on cultural fit, food environment, affordability, and digital behavior 
supports layered with pharmacotherapy (e.g., metformin, SGLT2 inhibitors, incretin-based agents). This review 
synthesizes mechanisms and comparative effectiveness from CR to precision diets, outlines practical protocols, 
and proposes a decision framework for matching people to sustainable nutrition that delivers durable glycemic 
control and cardiometabolic risk reduction.