This story is actually entitled Slimmer! by all official sources.
Talk about it here.
Slimmer! was the Doctor Who back-up strip which appeared in the pages of The Incredible Hulk Presents #11. Like all in the series, it was monochromatic and featured the Seventh Doctor travelling alone at the beginning and ending of the story.
Unlike most Doctor Who comic stories published by Marvel UK, Slimmer had a light, comedic tone that bordered on parody.
The Doctor decides to go to Weight-A-Way, "the health club at the edge of the galaxy", a place that fills him with dread. Nevertheless, he checks in with the receptionist for his "nine hundred and fifty year checkup".
After some preliminary fitness exams, the Doctor goes exploring. He discovers that other "guests" are being killed. Before he can protest, the receptionist brings him in front of the Gromungus, the universe's biggest glutton. The great blob has been eating all the club's clients, including the unfortunate Mr Bouillabaise, whose death the Doctor has just witnessed.
Seeing the Doctor, the Gromungus' appetite soars. At last he will have a meal free of fat, unlike his usual Weight-A-Way fare. Thinking quickly, the Doctor makes him a counter-proposal. By linking the Gromungus' room to the TARDIS, the Time Lord can provide his captor with entrées from across space and time. The Gromungus greedily agrees, and is swiftly supplied with an endless supply of food.
Soon, however, it becomes apparent the beast been tricked. He has eaten so much that his mass has increased to the point of gravitational collapse, causing him to become a black hole.
to be added
- Due to the parodic nature of the narrative, it featured numerous references to comedic literature.