NBC’s hit program The Biggest Loser shocked its TV audience last week when it revealed that the winner, Rachel Frederickson, dropped nearly 155 pounds, or almost 60 percent of her starting body weight, during the course of the program, Time.com reports.

The article questioned whether Frederickson’s speedy weight loss from nearly 260 pounds down to 105 was really safe, and what physically happens to the human body when it shrinks down to half its size.

Frederickson’s new height to weight ratio, or body mass index (BMI), put her slightly below the threshold of what most doctors consider a “healthy” weight, so if you thought The Biggest Loser winner looked a bit too skinny, you’re right.

Still, trimming down does hold a number of health benefits. Weight loss experts say Frederickson’s first 20 to 35 pounds would have been accompanied with immediate improvements to her blood pressure, blood sugar and breathing. What’s more, with each additional pound a person loses, physicians can see improvements in virtually every organ system in the body.

Frederickson’s appetite also probably changed for the better. That’s because swapping out foods such as white breads and chips with more complex carbs from beans, veggies and whole grains tends to make people feel less hungry and more satisfied with less food.

In addition, doctors suggest that the mental health effects for Frederickson might have been immeasurable. Studies show that when people go on a healthy diet, the neurotransmitters in their brain work better. Another benefit to Frederickson includes not being subjected to the stigma our society levels against people who are obese.

But health experts say Frederickson and her fellow competitors who lose large chunks of weight may still have work to continue healing their bodies. Serious health problems, such as heart issues, valve dilations and diabetes, must still be addressed long after the pounds melt away.

For Frederickson, physical therapy may also be needed to help repair her muscle and skeletal systems. Our bodies aren’t meant to carry a lot of excess weight, and Frederickson’s lower extremities probably underwent a significant amount of stress when she was working out while overweight.

TV stars use a wide array of fitness and diet techniques to shed pounds fast, but are they always healthy? Click here to read Real Health’s breakdown of four top celebrity weight-loss plans, including their risks and benefits.