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.
Complete a level with no Muffins collected
Play for 10 minutes
Collect 128 Muffins
Slash 200 wooden tiles
Collect 64 Muffins
Complete your first level
Collect 256 Muffins
Collect 512 Muffins
Collect 1024 Muffins
Complete World 1
Complete World 2
Complete World 3
Complete All Bonus Levels
Unscrew 100 screws
Teleport 50 times
Eat 25 chewing gum
Change Gravity 50 times
Change Gravity 25 times in one level
Hit Laser 50 times
Destroy 50 Uranium tiles
Unlock 50 costumes
Hit the Ground 50 times
Use motor 25 times
Travel in a basket 25 times
Cut 25 baskets
Hit 25 spikes
Complete World 4
Unlock 65 Costumes
Unlock 80 Costumes
Use Catapult 25 times