Osteosarcopenic obesity syndrome (OSO) has recently been identified as a condition encompassing osteopenia/osteoporosis, sarcopenia and obesity. OSO is especially deleterious in older adults (even if they are not obese by conventional measures), due to age-related redistribution of fat and its infiltration into bone and muscle. Osteoporosis and bone fractures in elderly increase the risk of sarcopenia, which, through decreased mobility, increases the risk of more falls and fractures, creating a vicious cycle. Obesity plays a dual role: to a certain extent, it promotes bone and muscle gains through mechanical loading; in contrast, increased adiposity is also a source of pro-inflammatory cytokines and other endocrine factors that impair bone and muscle. As the elderly population increases, changes in lifestyle to delay the onset of OSO, or prevent OSO, are warranted. Among these changes, dietary patterns and physical activity modifications are the first ones to be implemented. The typical Western diet (and lifestyle) promotes several chronic diseases including OSO, by facilitating a pro-inflammatory state, largely via the imbalance in omega-6/omega-3 fatty acid ratio and low-fiber and high-processed food consumption. Nutritional modifications to prevent and/or alleviate the OSO syndrome include adequate intake of protein, calcium, magnesium and vitamin D and increasing consumptions of foods containing omega-3 polyunsaturated fatty acids and fiber. Certain types of physical activity, often decreased in overweight/obese women and in elderly, might preserve bone and muscle, as well as help in reducing body fat accrual and fat infiltration. Habitual daily activities and some alternative modes of exercise may be more appropriate for older adults and play a crucial role in preventing bone and muscle loss and maintaining optimal weight. In conclusion, older adults who suffer from OSO syndrome may benefit from combined efforts to improve diet and physical activity, and such recommendations should be fostered as part of public health programs.