Christina Kimball can't wait to go under the knife.

The Movement Mortgage loan officer in northern California is giving one of her kidneys to a friend at her church. She is donating a part of her body simply because he needs one and she can.

"It was just that seeing him — we sit behind them in church — with his little girl sitting on his lap with her head on her daddy's shoulder, and he's sitting there with no strength and energy, it tugs on my heart," says Christina, 44. "God was telling me, 'You need to try.'"

In the operating room March 7, Clayton McCombe's life will change forever. But getting to the place to be able to give up part of her body has changed Christina's life as well. Most significantly, she's lost 40 pounds to get ready for surgery.

I would have never thought I'd be this excited to give up a part of my body, an organ, but I am.” – Christina Kimball

God has given her the peace she needs. You could say she has a peace that surpasses all understanding.

Stepping up

Donating a kidney wasn't even Christina's idea. At first, her husband, Eric, thought he could help the friend he met at Shiloh Delta Valley Church in Stockton, Calif.

Clayton, a 41-year-old medical insurance agent, has been dealing with health issues his whole life. A genetic condition that started in his liver moved to his kidneys, causing polycystic kidney disease.

When he had lost 70 percent of the function of his kidneys, he wanted to get on the transplant list right away. Although he was sick, he wasn't sick enough to be eligible for the list.

There are more than 800,000 people waiting for a kidney, according to the Living Kidney Donor Network. It takes about five years to get one, and usually they come from cadavers, even though the organs do not last nearly as long. Desperate to avoid dialysis, Clayton took matters into his own hands and put out a plea on Facebook for a kidney.

That's when Eric investigated if he was a match. But friendship could not top biology.

After Eric was rejected, Christina felt the call to see if she could help.

"It's humbling, to say the least, that someone would do that for you," says Clayton. "It's incredible, but it's still very, very weird. It's a good weird."

Bacon-shaped roses, anyone?

She passed the first round, a blood test.

The second round was even more intense, involving 24 hours of urine collection. The self-proclaimed neat-freak was not excited about storing her own urine in her own fridge. She made it, and more importantly, she was cleared to continue to see if she was a match.

However, there was a hurdle. Christina had to lose 40 pounds to be eligible to donate her kidney.

"That's the hardest part for me," she says. "I've always struggled to lose weight. I don't have a sweet tooth, all my teeth are sweet teeth."

At first, doctors said to get below 200 pounds when the scale was sitting at 215. Although a challenge, about a year ago she adopted a keto-style diet — meaning low-carb, high-protein. She lost 20 pounds and sailed through the second round of testing.

"It was all day testing. If anything was wrong with me, they would have found it," she says. "I was poked and prodded and had to pee in a cup again. But one good thing came out of it. One of the doctors wrote in my chart, 'looks younger than she is.'"

Although she was cleared medically to donate her kidney, her doctors had one more request: drop another 20 pounds.

"Why did they not just tell me that from the get-go?" she wonders, with slight exasperation in her voice.

She got the news last fall, which meant during the holidays, she returned to the keto diet and again found success. Now, the surgery is scheduled for March 7. But between getting the operation on the books and now, she gained 10 pounds. She's working to get back down to 180, determined to do so and keep the weight off even after surgery.

For Valentine's Day, she reminded her husband to leave the candy at the store. It's not allowed on her keto diet. She can have bacon, though.

A willing sacrifice

She's motivated to get control of her health for Clayton. He's in pain from his kidneys, which are about twice the size they should be but only work at 10 percent capacity.

The kidneys, normally the size of a fist, filter blood and make urine. Because they don't work correctly, Clayton suffers from swelling, pain, exhaustion and sensitivity to the cold. He has to watch what he eats, keeping in check his protein level to avoid gout, and potassium and sodium levels to keep his blood pressure normal.

After the surgery, he'll have to go on immunosuppressants for the rest of his life, to ensure his body doesn't reject Christina's organ. That means he'll be susceptible to disease and infection. He'll have to wash his hands more often and keep his environment clean, but with a functioning kidney, he'll be able to eat a normal diet. And although he doesn't know what it means yet, he does look forward to more energy.

Everybody tells me I'll feel normal again. I don't remember what normal feels like.” – Clayton McCombe

He looks forward to continuing to work with his church, Shiloh Delta Valley Church, where he is an associate pastor, with his wife Melissa and their two kids Miles, 7 and Mila, 4.

Where once they were just acquaintances, now a real bond has formed for the two couples. They even went on vacation to Hawaii together.

"She's my angel. I'm eternally grateful," Clayton says of Christina.

Christina, a former Keller Williams Realtor who joined Movement this past June, brushes off the huge sacrifice she is making.

"I'm thankful because one, I have peace about it, two, I'm excited about it and three it doesn't feel like a big deal," she says.