Lactate is the byproduct of glucose utilization by muscle cells and is a key regulator of intermediary metabolism, regulating substrate utilization. Lactate decreases and inhibits the breakdown of fat for energy purposes (lipolysis) as well as it can also interfere and decrease the rate of glucose utilization by cells (glycolysis). Also, lactate is crucial for the brain as lactate is the main fuel that neurons use and it is essential for long-term memory and could even be involved Alzheimer’s disease. Some studies show that when lactate uptake by neurons is suppressed, long-term memory is inhibited. Lactate could also be involved in some chronic metabolic diseases like type 2 diabetes as blood lactate levels in this population are 2-3 times higher than in healthy physically active population and it could be a major player in this disease. Cancer cells have a disrupted metabolism utilizing too much glucose aerobically (Warburg effect) and producing large amounts of lactate which could contribute to tumor growth and progression. Therefore, lactate is not just a waste product of anaerobic exercise but a major fuel and a key regulator of metabolism and its role in the possible epicenter of different chronic diseases is starting to be investigated.