Reduced food intake, avoiding malnutrition, can ameliorate aging and aging-associated diseases in invertebrate model organisms, rodents, primates and humans. Recent findings indicate that meal timing is crucial, with both intermittent fasting and adjusted diurnal rhythm of feeding improving health and function. Lowered intake of particular nutrients, rather than of overall calories, is also key, with protein and specific amino acids playing prominent roles. Nutritional modulation of the microbiome can also be important. The metabolic, molecular and cellular mechanisms that mediate the responses of health during aging to diet, and genetic variation in response to diet, are being identified and must be implemented in clinical practice. Indeed, billions of dollars are spent every year to treat highly prevalent diseases, such as heart disease, stroke, T2DM, hypertension, and obesity (among many others) which are largely prevent able with the implementation of the best healthy lifestyle practices.