Obese older adults will be randomized to participate in either healthy lifestyle intervention or behavioral diet and exercise intervention for one year. This study aims to determine the effects of Lifestyle intervention on bone microarchitecture, bone strength, bone material properties, and the mechanism behind it.

Previous studies had suggested that lifestyle therapy (diet plus exercise) resulting in weight loss in elderly population improves physical function, cardio metabolic risk factors, and cognition/quality of life, but a major complication is loss of BMD. The addition of exercise to diet-induced weight loss attenuated but did not eliminate weight-loss-induced reduction of BMD. Moreover, while long-term maintenance of weight loss and physical function was feasible, sustained lifestyle change led to continued loss of hip BMD, which might predict hip fractures. Although similar BMD loss with weight loss has been observed in younger populations, BMD loss in older adults might be of particular concern because of aggravation of age-related bone loss. Moreover, the belief that obesity protects against fractures has now been challenged by studies demonstrating that obesity is associated with poor bone quality and ankle and leg fractures.Because of previous lack of options to assess bone quality in vivo, there has been little or no scientific study of the possibility that lifestyle therapy in obese older adults improves bone quality. This study represents an unprecedented opportunity to prove the hypothesis that lifestyle therapy intervention improves bone quality and thus, may confer a protective rather than adverse effect on bone health. This will be the first randomized controlled trial (RCT) to comprehensively assess bone quality using novel techniques in response to lifestyle therapy in obese older adults, with major ramifications with regards to defining optimal treatment strategies for this increasingly high-risk older population.

Inclusion Criteria:

• Age 65 - 85 years • BMI 30 kg/m2 or more• Stable body weight (±2 kg) during the past 6 months • Sedentary (regular exercise <1 h/wk. or <2 x/wk. for the last 6 months) • Willing to provide informed consent

Exclusion Criteria:

• Failure to provide informed consent.
• Any major chronic diseases, or any condition that would interfere with exercise or dietary restriction, in which exercise or dietary restrictions are contraindicated, or that would interfere with interpretation of results
• Cardiopulmonary disease (e.g. recent myocardial infarction, unstable angina, stroke) or unstable disease (e.g., New York Heart Class III or IV congestive heart failure, severe pulmonary disease requiring steroid pills or the use of supplemental oxygen ) that would contraindicate exercise or dietary restriction
• Severe orthopedic (e.g. awaiting joint replacement) and/or neuromuscular (e.g. multiple sclerosis, amyotrophic lateral sclerosis, active rheumatoid arthritis) disease or impairments that would contraindicate participation in exercise
• Other significant co-morbid disease that would impair ability to participate in the exercise-based intervention (e.g. renal failure on hemodialysis, severe psychiatric disorder [e.g. bipolar, schizophrenia], excess alcohol use [more than14 drinks per week])
• Severe visual or hearing impairments that would interfere with following directions
• Significant cognitive impairment, defined as a known diagnosis of dementia or positive screening test for dementia using the Mini-Mental State Exam score less than 24)
• Uncontrolled hypertension (BP>160/90 mm Hg)
• History of malignancy during the past 5 years (except non-melanoma skin cancers)
• Current use of bone acting drugs (e.g. use of estrogen, or androgen containing compound, raloxifene, calcitonin, parathyroid hormone during the past year or bisphosphonates during the last two years)
• Osteoporosis (T-score -2.5 and below on hip or spine scan) or history of fragility fractures - Diabetes mellitus requiring insulin for treatment or with a fasting blood glucose of >140 mg/dl, and/or HbA1c >8.5% (Those excluded from the study because of fasting blood glucose of >140 mg/dl or HbA1c>8.5% will be referred to their primary care provider for follow-up and appropriate treatment).
• Terminal illness with life expectancy less than 12 months, as determined by a physician
• Use of any drugs or natural products designed to induce weight loss within past three months.
• Positive exercise stress test for ischemia