If you don't want to appear insensitive or mean word your conversation with this person with compassion and "I" statements. Stick to how you "FEEL" i.e. worried and not how you "think". For example anxiety is a feeling, "I feel you are too fat" is a thought, as a matter of fact a judgment, and NOT a feeling, even though the word "feel" is in the sentence.

Avoid sentences that begin with "you".

State your observations, which are facts, specifically and with out judgment. For example, saying "You have gained a lot of weight recently" - will put the person on the defensive, the statement begins with "you", has a judgment and the term "a lot" is purely subjective. By contrast saying "I feeling frightened" owns that the problem is yours, and states only your feelings.

Consider the fact that a person with many health issues may be worried themselves about the weight gain, unhappy, frustrated. They probably don't want to be judged. They probably want someone with whom they could share their feelings of rage and unhappiness. The old Buddhist saying "Don't just do something, sit there" would be helpful

Putting on weight may not always indicate a food addiction.
Some people who are depressed tend to overeat, as they feel good while eating, then guilty afterwards.
If a person has multiple medical problems and is gaining weight, a suggestion that they bring it up with their primary physician would be wise. Perhaps a statement like, "did you know many medications can make you gain weight, even if you are not eating more" would be a gentle way of letting someone know it is OK to ask for help.
Most likely the person is well aware of the weight gain, but may feel overwhelmed with life to deal with the weight issue at this time. Going for walks and gentle exercise may be one way to motivate the person to be more concerned about the weight gain.