Obesity is a central health issue due to its epidemic prevalence and its association with type 2 diabetes and other comorbidities. Obesity is not just being overweight. It is a metabolic disorder due to the accumulation of excess dietary calories into visceral fat and the release of high concentrations of free fatty acids into various organs. It represents a state of chronic oxidative stress and low-grade inflammation whose intermediary molecules may include leptin, adiponectin and cytokines. It may progress to hyperglycemia, leading to type 2 diabetes. Whether or not dietary antioxidant supplements are useful in the management of obesity and type 2 diabetes is discussed in this review. Only the benefits for obesity and diabetes are examined here. Other health benefits of antioxidants are not considered. There are difficulties in comparing studies in this field because they differ in the time frame, participants' ethnicity, administration of antioxidant supplements, and even in how obesity was measured. However, the literature presents reasonable evidence for marginal benefits of supplementation with zinc, lipoic acid, carnitine, cinnamon, green tea, and possibly vitamin C plus E, although the evidence is much weaker for omega-3 polyunsaturated fatty acids, coenzyme Q10, green coffee, resveratrol, or lycopene. Overall, antioxidant supplements are not a panacea to compensate for a fast-food and video-game way of living, but antioxidant-rich foods are recommended as part of the lifestyle. Such antioxidant foods are commonly available.