When someone says that to me, I feel that they are asking for help, guidance maybe, in a not-so-direct way. As if to say, "I see that I need to lose weight, but I haven't been able to do anything about it." Even when I say it to myself, I am stating the obvious.
When someone says that to me, the first thing I do is jump in and ask them, Have you tried this? - Have you tried that? I think what they really need me to ask them is "How can I help you do that?" Maybe they just need me to listen.
I've learned that when I get critical of myself like that, I just jump in and do something about it; to start with something small and take a conscious step. For example, choosing to wake up 30 minutes earlier so I can walk for 20 minutes. Or making a different decision about what I choose to put in my mouth for a meal. It can be as simple as that. When I start to change these simple physical things, it changes my emotional state too. I am kind and gentle with myself.