Here is the full list of all 30 Cat on a Diet achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Unlock 80 Costumes
Unlock 65 Costumes
Collect 1024 Muffins
Change Gravity 25 times in one level
Teleport 50 times
Hit the Ground 50 times
Hit Laser 50 times
Hit 25 spikes
Cut 25 baskets
Unscrew 100 screws
Destroy 50 Uranium tiles
Unlock 50 costumes
Complete All Bonus Levels
Complete World 4
Use Catapult 25 times
Collect 512 Muffins
Complete World 3
Change Gravity 50 times
Travel in a basket 25 times
Complete World 2
Eat 25 chewing gum
Collect 256 Muffins
Complete World 1
Use motor 25 times
Slash 200 wooden tiles
Collect 128 Muffins
Play for 10 minutes
Collect 64 Muffins
Complete a level with no Muffins collected
Complete your first level