Lifestyle disorders such as diabetes, obesity, cardiovascular disease, cancer, and gastrointestinal dysfunction have become leading causes of morbidity and mortality worldwide. Diet plays a central role in the prevention and management of these conditions, with growing emphasis on functional foods rich in bioactive compounds. Millets, a group of climate-resilient small grains, have gained prominence as sustainable foods with significant therapeutic potential. Their high content of complex carbohydrates, dietary fiber, resistant starch, and phytochemicals including phenolic acids, flavonoids, and lignans contributes to improved glycemic control, lipid regulation, gut health, and immune modulation. Evidence from preclinical and clinical studies demonstrates that millet consumption lowers postprandial glucose, enhances satiety, reduces systemic inflammation, and supports favorable shifts in gut microbiota. Fermentation of millet fibers yields short-chain fatty acids such as butyrate, which exert anti-inflammatory and anticancer effects by strengthening gut barrier function and promoting apoptosis in malignant cells. Additionally, the rich mineral profile of millets, including magnesium, iron, zinc, and selenium, supports metabolic balance and immune defense. Collectively, this chapter highlights the nutritional benefits of millets in addressing lifestyle-related diseases while also underscoring their role as sustainable foods for global nutrition security.