Mitochondria are the powerhouses of the cell, and they are fuel flexible. They can generate power from nearly every abundant carbon source in the body, including carbohydrates, amino acids, and fatty acids. When mitochondria are sick, however, some fuels may be better than others – and the best may not come in “heart healthy” packaging. In this issue of EMBO Molecular Medicine, Southwell et al, report dramatic rescue of a mitochondrial cardiomyopathy by forcing sick mitochondria to use fatty acids, delivered through a high fat diet, rather than sweet glucose they seem to prefer.