To evaluate the therapeutic efficacy and metabolic impact of a low energy diet (LED) in people with familial partial lipodystrophy and diabetes. Participants will be provided with a LED (total diet replacement) for 12 weeks, before the introduction of a stepped food transition. Metabolic effects will continue to be assessed for 1 year. In order to better understand why this intervention changes insulin sensitivity, we will also collect adipose and muscle tissue samples at baseline and 12 weeks into the intervention in participants willing to have these procedures performed. These samples will be used for histological, metabolite, gene expression and protein expression analyses.