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
Hit Laser 50 times
Cut 25 baskets
Hit 25 spikes
Teleport 50 times
Unlock 65 Costumes
Complete All Bonus Levels
Complete World 4
Collect 1024 Muffins
Change Gravity 25 times in one level
Use Catapult 25 times
Unlock 50 costumes
Complete World 3
Destroy 50 Uranium tiles
Complete a level with no Muffins collected
Change Gravity 50 times
Complete World 2
Unscrew 100 screws
Collect 512 Muffins
Hit the Ground 50 times
Travel in a basket 25 times
Eat 25 chewing gum
Complete World 1
Collect 256 Muffins
Use motor 25 times
Collect 128 Muffins
Slash 200 wooden tiles
Play for 10 minutes
Collect 64 Muffins
Complete your first level