Justin was a nerdy 22 year old college student, shaggy and unkempt brown hair, thick glasses, average height, and packing a belly that had gotten out of hand. Justin wanted a change, he was tired of being overweight and ignored by all women, and decided that working out would be a good place to try next.

Justin followed his normal methods of information gathering before starting a new assignment, a trip by the used book store. He admittedly knew nothing about working out nor healthy dieting. His first attempts at weight loss were largely fad diets that had ended with no change to his waist line or him actually putting on more weight. With any luck, The used book store would have something that would actually help.

After browsing for a good hour, and finding some great science fiction books he’d been eyeing, Justin made his way to nutrition and exercise section. Before him stood a wall of books covered with pictures of men and women in amazing shape, body builders, sports professionals, and plenty of books by “doctors” claiming to offer quick results. The sight was overwhelming at first, largely because it was Justin’s first time in his section. He didn’t know where to even start. A large brown book with strange writing stuck out. It felt like it didn’t belong here and it looked older than any of the sci-fi books that he had read.

Out of curiosity, he grabbed it and held it in his hands. Opening it, he instantly realized it was a non English book. Dismayed, he flipped through the pages to look for any illustrations that may be useful even if the words weren’t. As he flipped through, he noticed that a page was in English.

It appeared to be a recipe for a protein bar, one that claimed to make someone as strong as an ass. Justin loved every word of it but the last which confused him. ‘Strong as an ass? Like a donkey?’ Hoping his assumption was correct and the recipe would help him build muscle, he bought the book and went home.

In his kitchen, Justin started reading the ingredients. This turned out to be a challenging task because for some reason he could only read one line at a time and it took his eyes a second to understand the words when he looked at them. Justin paid this no mind though, he was probably more tired than he thought he was and he was making progress.

Once he finally finished the list, he realized that he had all of the ingredients handy, even the more unusual ones like dry grass and sweat from a gym sock, which his jock roommate could provide. He got to work mixing the ingredients, anxious to try it out. The final instruction was weird but strangely it turned him on, the book told Justin that when forming the bars and while baking them, he must be wearing nothing but a dirty gym jock. Justin had already realized that he was working with magic, but why a dirty jock? The point wasn’t important, if Justin wanted this to work, which he really wanted, he would have to follow all the instructions.

After returning from his jock roommates room for a second time, Justin stripped off his clothes and put on the dirty and smelly jock. Despite being grossed out, Justin formed the bars and placed them in the oven for 20 min. While they baked, Justin saw a small footnote that held a warning, “Warning: consumption may lead to addictive tendencies towards this item. Continued ingestion may lead to permanent alterations.”

Justin laughed, of course he wanted these changes to be permanent. If this worked, he probably would never want to return to being a weak nerd. And besides, he was starting to get used to wearing a dirty jock around the house.

Before he knew it, the timer on the oven sounded and Justin pulled out the bars. They didn’t look very edible, but how else is one supposed to get something without some sacrifice. Justin grabbed the first bar and began eating it, noting that it tasted a lot better than it looked. Even the strong taste of feet and cock didn’t bother him like he thought it would.

Justin quickly snapped a before picture, still wearing his roommates dirty jock, to keep as a before picture. Just after snapping the pic, he noticed that he was getting hard, very hard, and in fact his cock was growing. Before long it forced itself out of the jock, showing no signs of slowing down. Justin watched with amazement, not realized that it was now 20 in long and getting a flat head like a donkeys cock nor that this might be bad.

Justin opened his mouth to make a dumb comment on the growth, only to have a bray leave his mouth in stead of words. This too didn’t seem to bother him, if anything it turned him on more and convinced him to start stroking his now 29 inch donkey cock, letting out brays of pleasure as he did. Justin’s mind started growing fuzzy as he stroked. Memories of books, school, and other nerdy things began to disappear form his mind, slowly being replaced by the gym, being a donkey boy, and cock. Lots of cock. Cocks fucking his ass. Cocks going down his throat. And cocks lining up to fill his empty holes.

Justin’s ears started feeling weird next as they started growing pointy and hairy. Even this didn’t worry the horny Justin. What Justin did notice was that his muscles were growing, his fat was slowly melting away, hair was growing on his body making him more manly, or maybe more donkey. The latter seemed to turn him on more as he felt a tail start to grow over his ass.

The tail was too much for Justin and he felt himself buckle was he was about to cum. Another bray left his mouth as thick jets of donkey cum covered the mirror before him.

Justin breathed hard as he slowly regained his ability to speak, the tail and ears disappeared, the hair on his body started resembling human hair instead of fur, and his mind refilled with some of his old thoughts. His big donkey cock also shrank down to be about 10 inches, though still shaped like a donkey’s and Justin liked that.

The experience left Justin exhausted, way too tired to try eating another. He’d save the rest of them for a later date and besides, it was getting late and he needed to get some rest. An unusual thought crossed his mind though, his jock roommate Kevin would be home soon, and he was always looking for an ass to fuck. With any luck, Kevin would like Justin’s new and improved, though not perfect, body. This thought won Justin over and he went to lay on Kevin’s bed, waiting for the jock to come home and fuck him.