Fat Pokémon Species

Snorlax is the Sleeping Pokémon, and is the heaviest Normal-type Pokémon. Its body is round, and its belly takes up most of its body. It has undeveloped legs, and its arms are only somewhat thick.

It is mostly seen sleeping and rarely wakes up, and when it is awake, it is usually to eat about 900 whole pounds of food for the day, or 400 kilograms, and then goes back to sleep. It gradually gains weight and becomes more slothful over time. Its stomach is strong enough to allow it to eat moldy items or even thorny plants and Muk's poison without suffering any ill effects. It is also able to eat while resting. As expected, it can have the Gluttony and Thick Fat abilities.

Like Garbodor, Snorlax has a Gigantamax form where it hardly moves, when it battle it barely moves its arm.

Lickilicky is a round and roughly humanoid Pokémon, to the point it is nearly spherical. It has a small tail, very small legs, and small arms. It looks like it could accidently roll around if it falls over in a certain way.
An average Lickilicky is 5 feet 7 inches tall, making it similar in size to an adult human, and their average weight is about 308.6 pounds, or 140 kilograms. Its appetite is large, and it licks objects and people for extra crumbs. Its saliva is able to dissolve nearly anything. Despite this, it does not have the Thick Fat or Gluttony abilities.

Purugly is a fatty cat, weighting nearly 100 pounds, or exactly 43.8 kilograms, and is only 3 feet and 3 inches tall. It also has a crude appearance, with zigzag whiskers, purple tipped ears, and a spring tail. Its legs appear to be thick and developed.
It wraps its tail fluff around its belly to compress it like a corset, to appear larger and bulkier. Removing its tail from its belly will result in its belly expanding, showing its actual body proportions. This happens when fainting in Pokémon Battle Revolution and in the Pokémon anime series.
As expected, it can have the Thick Fat ability, but it is unexpectantly fast with high speed stats.

Garbodor is a large and fat looking heap of trash. Its body is round and lumpy, and has no proper legs, only feet. Its two asymmetrical arms are not thick, however. It starts out around six feet in height and can devour garbage to grow even larger.

Unlike the other Pokémon on the list, it has few of the tropes of the fat Pokémon, as it does not have the Thick Fat or Gluttony abilities, and is not described to be gluttonous or lazy.
It has a Gigantamax form, which makes it significantly larger and turn into a legless and footless mountain of trash, acquiring discarded toys on its body.

Greedent is a plump squirrel like Greedy Pokémon. Its brown body is somewhat round, and it has a massive tail.
As its name and categorization suggests, it is incredibly greedy and gluttonous, and eats a lot of berries to the point it is commonly found around berry trees. Its signature move Stuff Cheeks involves it eating its own held berry. It has the hidden ability Gluttony, and its normal Cheek Pouch ability allows it to recover HP when consuming a held berry.
The excessive amount of berries it stuffs in its tail result in berries constantly falling out of its own tail, and even more fall off when hit or it faints. However, it is somewhat dumb, so it doesn't notice its berries falling out. Its behavior makes it likely to gain weight over time.

Slaking is categorized as the Lazy Pokémon, and its ape-like body is incredibly bulky and plump. Its arms and legs are slightly bulky.
It sleeps throughout most of the day, and will save its energy when lounging. It lazily rolls over when the food around it runs out. Its body weight is likely a result of it being incredibly lazy. Its only ability, Truant, triggers it to be lazy in battle, preventing it from moving every other turn.

While Appletun's neck and tail are not that large, it looks like it has a huge fat lump or hump on its back, making it look like a large apple pie blob or a fat green and yellow camel. Its limbs are small compared to this large hump.
It can have the Gluttony and Thick Fat abilities, suggesting that the huge hump on its back is a fat deposit. In addition, sweet nectar is caked on its body.

Its fatty body and cheeks give Alolan Raticate an appearance of being a fat Pokémon, especially compared to its original Kanto origin counterpart. It has what appears to be a pot belly, and its cheeks are circular and look like they are partially covering their mouth.
Alolan Raticate have a higher calorie diet than regular Raticate. They use their nest as a food stockpile, and would rather have their Alolan Ratatta underlings search for food and remain at their nest and eat the food they bring. It can have the abilities Thick Fat and Gluttony. It also has a Totem-sized version, which is of course taller and heavier.

Hariyama is a sumo wrestler based Pokémon. In real life, sumo wrestlers train to increase their muscle mass and adipose tissue mass so that they are harder to move, and have more weight to push others with. It appears to be a very heavy humanoid with bulky thighs and a large torso.
Generally, it is easier to gain significant amounts of body fat than to increase muscle mass, thus most real life sumo wrestlers appear very fat. However, Hariyama's body is described to be made of mostly muscle, not fat, though it can have the Thick Fat ability.

Jynx, the Human Shape Pokemon, appears as an overweight humanoid, and can be compared to an opera singer.

wailmer, the beach ball pokemon

Mamoswine is a large pig like Pokémon who appears incredibly bulky. As a pig, it is likely that its body shape is caused by body fat. It has the ability Thick Fat as well.

Sealeo is a large and plump walrus like Pokémon. Its body jiggles in games such as Pokémon Colosseum, suggesting that its body is padded with blubber. It has the ability Thick Fat as well.