In our previous study, we have observed that: 1) nearly half ALL patients are overweight or obese at diagnosis, 2) all patients, regardless of starting weight, gain significant fat mass over the first month of therapy (on average 20-30%), and 3) obesity at the time of diagnosis is associated with a higher likelihood of poor response to chemotherapy as evidenced by persistent leukemia (minimal residual disease) after induction therapy. Together, these data show that body fat is a significant risk factor for ALL treatment failure, and that its negative effects are evident within the first month of treatment. Recent laboratory and clinical data illustrates the ability of diet restriction and physical activity to improve chemotherapy efficacy, reduce treatment-related toxicities and better overall quality of life.