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