We'll Grow Thin Together (1979)

Victor (Sir Peter Ustinov) is a screenwriter whose last work about the Marechal Pétain is refused by his producer. To add insult to injury, he tells Victor he is paunchy. The unfortunate man becomes obsessed by his weight. He goes out of his way to lose pounds, abetted by his wife, Corinne (Bernadette Lafont), who puts him on a diet. He must also go to a health center where he takes exercise. Nothing really works. One day, in a brewery, he cannot stand his diet anymore, and he has a gastronomic meal. Desperate, he tries his luck at a Weight Watchers reunion.