How do you tell a loved one that they need to loose weight

I would take this person out for a coffee and ask them if they are ok. Do they need any support....are things OK.

Weight is connected with emotions.

I told my husband, after trying to gently nudge him into losing his tummy, that he looked more pregnant than I did when I was at delivery point. I also pointed out that not only was this not very sexy but it was extremely dangerous for his health and I wanted to keep him for a bit longer.
It is now half the size and shrinking!.
Maybe this approach only works on husbands

What sort of family member?

I am inclined to agree with most posters that you're better to keep quiet because the person will already know they are overweight.

Perhaps it is different with a partner or offspring. Much depends on their general health, personality and how you get on with them in the first place.

With some people, home truths work but I really would think very carefully. You don't want to have a terrible argument.

Sometimes medication can promote weight gain, difficult one to tackle but informing a family member that you are concerned with their weight issues may not be the best action to pursue.