An Appetite for Battle! (Japanese: ハリマロンVSマフォクシー！ダイエットバトル！？Harimaron VS Mafoxy! A Diet Battle!?) is the 15th episode of the XY series, and the 814th episode of the Pokémon anime. It first aired in Japan on February 6, 2014 and in the United States on April 26, 2014.
On their way to Cyllage City, our heroes decide to camp out for the night. Clemont puts his inventor skills to use making an excellent dinner. And for dessert, Serena brings out a basket full of her homemade macarons—but the basket is empty! Clemont quickly discovers that his Chespin has eaten them all...again!
Clemont apologizes to the others and tries to get Chespin to battle Ash’s Froakie for some exercise. But after eating all those sweets, Chespin is completely stuffed and moving slowly, and Froakie beats it easily. Bonnie challenges them next, and Dedenne wins in a flash. Chespin seems embarrassed, and Clemont is determined to get his Pokémon ready for battle again.
That night, Clemont is hard at work inventing some new exercise gear for Chespin. But he doesn’t realize Chespin has been lured away by the smell of something delicious. Still in a snooze, Chespin follows its nose through the woods to the steps of a house, where it falls asleep again.
The next morning, Chespin wakes to discover the source of the delicious smell: fresh macarons just out of the oven! Carrie, the old woman who lives in the house, is delighted to have such an enthusiastic audience and gives Chespin all the macarons it can eat. When Clemont comes looking for his wayward Pokémon, he sees Chespin happily munching macarons with Carrie on the porch and decides Chespin is better off right where it is.
When her husband Wylie returns home, Carrie asks Chespin to take her side in a battle against him and his Delphox. Going up against a powerful Fire-type Pokémon scares Chespin, especially since its very full belly is still making it hard to battle. Sure enough, Delphox’s first attack is a direct hit, and it sends up a cloud of smoke big enough for our heroes to see from a distance. Clemont realizes Chespin is in trouble and runs back to the house, throwing himself into the line of fire! Wylie quickly calls off the battle, but Chespin wants to keep going, so Clemont asks if he can step in.
It’s still a bad matchup, but Clemont figures out that since Chespin is rounder than usual right now, it’s particularly good at rolling. He tells Chespin to keep rolling and dodging Delphox’s attacks, and eventually Chespin starts to feel more like its usual self. Wylie is about to unleash a powerful move, despite his wife’s warnings—but in the midst of giving this dramatic order, he hurts his back! The battle is called to a draw, and Wylie and Carrie explain that the purpose of the battle was to settle an argument they had the day before. But it turns out Wylie already bought Carrie a lovely cake to apologize, and they decide to share it with our heroes as thanks for their help!
As Ash and his friends walk down a road at sunset, Serena mentions that they might not make it to a Pokémon Center before nightfall. Ash suggests they camp out for the night. Serena is hesitant to the idea, but once her friends offer her accommodations, she relaxes. At the camp, Clemont has prepared a meal for the group, who are impressed with his cooking skills. Serena offers macarons that she had baked earlier as dessert, but when the basket is opened, it is empty. While the kids wonder, it is revealed that Chespin has stolen the macarons to eat for itself. Clemont soon notices this and chases after Chespin, who crashes into the tent before swallowing the last macaron. As Serena and Ash fix the fallen tent, Clemont apologizes for what Chespin did, but the group reassures him it was no big deal. Ash suggests a battle to give the bloated Chespin some exercise, and Clemont agrees.
Ash uses Froakie and starts off the battle with Bubble. Clemont orders Chespin to dodge, but it is so full that it is too slow to avoid the attack. Clemont responds with Tackle, but Froakie easily dodges before ending the battle with Pound after Chespin's failed dodges. Bonnie teases that with Chespin in its current state, even her Dedenne can beat it, and Ash encourages them to battle. Clemont begins with Tackle, but Chespin slips and slides at Dedenne's feet, who electrocutes it for an easy win.
As the group starts going to bed, Clemont remains outside, determinedly building Chespin an exercise machine. While he works, Chespin follows an alluring smell into the forest. Clemont completes his machine, naming it the "Overeating Fat Reduction Exercise Gear." As morning comes and Chespin continues to wander away, the machine refuses to stop and classically explodes, prompting Serena, Ash, and Bonnie to leave their tents. Clemont finally notices Chespin's absence, so the group calls after it. Meanwhile, Chespin follows the smell to a house in which an old woman named Carrie is cooking. After Chespin falls asleep near the door, Carrie notices it and brings Chespin inside. Back at camp, Clemont worries that Chespin hates him because he forced it to battle.
When Chespin wakes up, Carrie has just finished baking macarons. She takes Chespin outside and lets it eat them, whereupon Clemont discovers the house and watches from the bushes. Clemont feels guilty for what he put Chespin through and walks away. When he returns to the group, Clemont tells the others that he let Chespin be because it looked happy. At the house, Carrie's husband Wylie has returned from a tournament. Hungry, he begins to grab a macaron, but his wife snatches them away, saying that he will have to battle her first if he wants to eat them. The husband is skeptical that his wife can beat him, but she says she has a secret weapon, Chespin. Wylie agrees, on the condition that the woman forgive him for what he said yesterday, to which his wife responds that on the account of her win, he apologizes.
Outside, Wylie brings out Delphox and tells it to use Will-O-Wisp, which creates a smoke cloud that alerts Ash and his friends. They rush to the scene and find Chespin in a losing battle. Serena uses her Pokédex to identify Delphox and realizes that Chespin is at a type disadvantage. When Delphox fires Flamethrower, Clemont intervenes and blocks it with his Aipom Arm. As the group runs over, Clemont explains to Carrie that Chespin is his Pokémon. Wylie announces that he won, but Chespin becomes determined to fight and Clemont takes control. Wylie begins again with Will-O-Wisp, and Clemont orders Chespin to roll, realizing it would be pointless to attack while Chespin is still full and that Chespin must first make its body lighter. As Chespin rolls, avoiding Delphox's attacks, its moves improve and it loses weight. Clemont orders it to use Tackle, after which Chespin is back to normal. Chespin then uses Vine Whip, but Delphox uses Flamethrower, and it appears that Chespin has fainted. Just then, Chespin struggles to its feet, activating its Overgrow Ability. Now with more strength, Chespin uses Vine Whip and knocks the stick out of Delphox's hand. Wylie decides to use his best move, Mystical Fire. Carrie tries to stop him from using the move, but while he is commanding it, his back cracks, and the battle is over.
Inside the house, the couple explain their quarrel. Wylie then brings out a cake he bought for his wife as an apology. The two make up, and suggest that they all eat the cake together. Afterward, Chespin explains that it did not run away because it hated Clemont, and the two reconcile. As the group walks on towards the next gym, they realize that they again will not make it to a Pokémon Center before dark. This time, Serena is the one who suggests they camp!