“Keto Crotch” got you down? No one said losing weight would be easy.

Yes, in some cases the pros — having a healthier heart, for example — outweigh the alarming cons, like, say, explosive diarrhea. But that doesn’t mean you shouldn’t be aware of the gross, weird, unexpected bodily malfunctions that can occur in the pursuit of weight loss.

Here, registered NYC dietitian Sammi Brondo, author of “The Essential Vegetable Cookbook,” explains the most uncomfortable side effects of popular diets.

Diarrhea

Low-carb diets, like keto, paleo or carnivory, can give you the runs. “We need soluble fiber… to bind food in the system,” Brondo says. The lack of it makes our stool less solid, Brondo explains.

“It’s relatively common,” but that doesn’t mean it’s a good thing, she says. “[It’s] totally not healthy.”

And while some people’s digestive systems might adjust over time, others may not be so lucky. In addition to the dreaded discomfort, repetitive bowel blowouts can affect the way your body absorbs vitamins and minerals.

“It’s a sign you need to add those carbs back in,” Brondo says.

Bad breath

Sure, “Keto Crotch” is stealing the spotlight recently — but let’s not forget that smell can drift upwards, resulting in some seriously stank breath. Without carbs in your body, you go through a process called ketosis, Brondo explains. “Certain chemicals are released in your breath, they have this fruity or metallic smell almost,” she says.

Sore Tongue

A lack of B12, a vitamin most commonly found in animal products, can cause difficulties for those eating vegan diets. Aside from more common symptoms, like anemia, missing this important nutrient in your diet can cause pale skin and a painful tongue.

Yes, you read that correctly.

At least this side effect has an easy fix: take B12. “A lot of cereals are fortified with B12,” says Brondo, offering one way to get the vitamin without eating animal products.

Passing gas

Greens, greens, they’re good for your heart. The more you eat, the more you fart. This is not a fun children’s rhyme, but a warning from a dietitian. For those attempting the “Cabbage Soup Diet,” beware.

“Cabbage has a specific enzyme that we don’t have,” Brondo says. “So we can’t break it down in our bodies, and that causes gas.”

Note: Chugging milk also is a surefire way to light up a room in a very wrong way.

Constipation

Not eating enough fiber — or eating too much fiber — can leave your booty backed up.

“You’ll get fiber from grains, fruits and vegetables,” Brondo says. Make sure to not take your high-fiber diets to the extreme or avoid grains, she says. “Fiber can get stuck in the body, and if you’re not drinking enough water or moving enough to keep things going, it can end up being constipating.”

This article originally appeared on the New York Post.