The Biggest Loser is an American competition reality show that initially ran on NBC for 17 seasons from 2004 to 2016 before moving to USA Network in 2020.^[3] The show features obese or overweight contestants competing to win a cash prize by losing the highest percentage of weight relative to their initial weight.

Each season of The Biggest Loser starts the 30-week competition with a weigh-in to determine the contestants' starting weights, which serve as the baseline for determining the overall winner.

The contestants are grouped into teams of three, each wearing separate colored T-shirts. Depending on the season a team may work with a specific trainer or all trainers may work with all contestants. The trainers are responsible (in conjunction with medical personnel retained by the show) for designing comprehensive workout and nutrition plans and teaching them to the contestants. However, the contestants are individually responsible for implementing the principles taught.

During an episode, various challenges and temptations (see below) are featured. Those who win a particular challenge are given special privileges, such as a weight advantage for the next weigh-in or even full immunity from being voted off the show.

Each week culminates in another weigh-in to determine which team has lost the most weight for that week, in percentage of total weight lost. The team that has lost the least percentage during that week (known as "falling below the yellow line", which refers to a line featured on a video screen showing the cutoff between safety and being at-risk) will have one member voted off (unless the team consists of only one remaining member, in which case there is no vote). The vote is usually made by the other teams, though some episodes feature one team making the decision alone. Some episodes feature a second, "red line"; if a contestant falls below the red line the contestant is automatically off the show with no vote. Other episodes allow for the contestants, if successfully meeting a goal at the weigh-in, to all receive immunity for the week.

When the number of contestants has shrunk to a predetermined smaller number (unknown to the contestants), the teams are dissolved and the contestants compete one-on-one against each other.

The season finale reunited the final contestants remaining on the show and those eliminated. The eliminated contestants compete for a smaller prize while those remaining on the show compete for a larger prize and the title of "The Biggest Loser".

Episodes are typically two hours long. Some episodes have been aired in a shortened one-hour format to accommodate adjacent network programming such as The Voice^[4] and the State of the Union address.^[5] Each episode features some, but not all, of the following activities (some contestants may not participate in an activity with physical requirements if placed on medical restrictions):

1. Temptation:
   Contestants prepare for the first day of the week only to find a situation that involves temptation. The temptation usually requires contestants to gamble by eating or drinking delicious but high-calorie foods in exchange for what may seem to be a beneficial trade-off. The benefits may or may not be known to the contestants in advance. Examples include eating sweet foods for a chance to call their loved ones, eating a big slice of cake to win an unknown prize (which, in one episode, turned out to be an exercise bike) or giving up time with a trainer for a chance to win money. Contestants are given a set period of time before the offer passes.
2. Reward Challenge:
   Contestants compete to win a prize, first as teams and then as individuals after the teams are dissolved. After the challenge, viewers are shown the winning team enjoying their reward while the losing team accepts their loss. Prizes range from immunity- which is exemption from elimination—to exercise equipment, phone calls home or weight prizes, which allow winners of a challenge to have a greater weight loss at the Weigh-In, or losers of a challenge to have a lower weight loss at the Weigh-In (e.g. a 6 lb weight loss would result in a 7 lb weight loss if a contestant were to win a "1 pound advantage" whereas it would result in a 5 lb weight loss if a contestant were to win a "1 pound disadvantage"). If there is an unequal number of players on each team, then the team(s) with more players must pick an individual or individuals who will sit out until there is an equal number of players on each team. Occasionally, players have to be cleared by the show's doctors in order to participate in physical challenges.
3. Initial Workout:
   Contestants work out with the trainers. During this segment, the trainers will often speak with certain contestants, especially those who are doing poorly. Usually, underlying emotional issues are revealed at this time (such as a loss of a family member or a physical calamity), often the triggering events that led to the weight gain in the first place.
4. Last Chance Workout:
   Last chance workouts are often shown as grueling, final preparations for the weigh in. This is a real test of strength and trainers push contestants to their limits.
5. Last Chance Challenge:
   Introduced in season seventeen, the last chance challenge is a variant between a reward challenge and a last chance workout. As with the last chance workout, the last chance challenge will usually take place inside the gym. The winning team will win a prize that benefits the team just before the upcoming weigh-in (for example, a two-pound weight advantage for the team).
6. Weigh-In:
   Although the show depicts the weigh-in in an evening setting, the actual weight measurement occurs off-camera in a morning session and the contestants are not told of the results at that time. All contestants are weighed to determine the amount they have lost relative to their total body weight. During team-based competition, the team that loses the highest percentage wins and the losing team must send one person home. When the teams are dissolved and the show becomes an individual competition, the two contestants who lose the lowest percentage of weight are below the yellow line and eligible for elimination. A similar setup to individual-based weigh-ins happens when the two initial teams are broken up into four teams of two or three, as happened in the second and fourth seasons. In season ten, the rules changed. The contestants are now expected to weigh in before challenges. The yellow line now increases up to half of the slots depending on how many contestants there are at the ranch. Contestants below the yellow line face an elimination challenge before the vote. In addition, the Biggest Loser of the week is allowed to save a person below the yellow line from elimination. Some episodes have featured both a yellow line and a red line; a contestant who falls below the red line is eliminated outright from the competition without a vote of the other contestants.
7. Elimination Challenge:
   Introduced in season nine, the elimination challenge was for the two people below the yellow line. In the only elimination challenge of that season, the longest one standing stayed while the other went home. In season ten, the elimination challenge was re-introduced. Those below the yellow line participate in a challenge to escape from the vote. The two least successful contestants face the vote.
8. The Vote:
   The final segment of the show takes place in a dining room that has refrigerators labeled with each contestant's name (active contestants have their name illuminated) and filled with that contestant's favorite tempting foods. Prior to the vote, contestants facing elimination plead their case as to why they should remain on the Ranch (several episodes feature contestants making a "sacrificial" request to be sent home, generally a team agreeing as to which member should stay and which one should go, or one contestant feeling that they can make progress at home while another needs the Ranch setting to continue his/her progress). The other contestants are not required to honor any requests to be sent home, though generally such requests are honored. The contestants facing elimination arrive at the dining room first; the other contestants each carry a covered plate containing the name of the person they wish to vote out. In the event of a tie, the contestant or team who lost the least percentage of weight is eliminated, except if both of the contestants or teams lost the least percentage of weight. As people are voted out, the light for their name is extinguished. After the vote, the eliminated contestant is shown at home and discusses the progress they made in their weight loss.

According to LiveScience.com, "physicians and nutritionists worry the show's focus on competitive weight loss is, at best, counterproductive and, at worst, dangerous".^[7] Contestants on the show lose upwards of 10 pounds per week (in the very first week, some contestants have lost 20–30+ pounds in that one week alone), whereas the established medical guidelines for safe weight loss are between 1 and 2 pounds per week.^[8]

Other health writers take it even further, suggesting that everything from the show's dietary guidelines to workout routines are completely flawed.^[9]

Nutritionist Dr. Barry Sears sums up the wellness paradox: "First, eating less can cause stress to the system causing more hunger. Second, the more people exercise, the hungrier they become." Dr. Sears continues by claiming that "even with the most intense training, people are unlikely to add more than five pounds of muscle in 12 weeks of weight training. The reason viewers see their muscles emerging as the show goes on is because as the layer of fat surrounding the muscles is lost, muscles become more visible. Those muscles were always there but covered by a mass of fat tissue.^[10]

At the end of every telecast, the following disclaimer is shown:^{[citation needed]}

Our contestants were supervised by doctors while participating in the show, and their diet and exercise regimen was tailored to their medical status and their specific needs. Consult with your own doctor before embarking on any diet or exercise program.

Despite this claim of supervision, however, all contestants are required to sign a waiver that states: "no warranty, representation or guarantee has been made as to the qualifications or credentials of the medical professionals who examine me or perform any procedures on me in connection with my participation in the series, or their ability to diagnose medical conditions that may affect my fitness to participate in the series".^[11]

The weight-loss regimen used in the show—severe caloric restriction combined with up to six hours a day of strenuous exercise—involves risks including a weakening of the heart muscle, irregular heartbeat and dangerous reductions in potassium and electrolytes.^[6] Contestants, regardless of their weight, are required to certify that they believe they are "in excellent physical, emotional, psychological and mental health".^[6]

The Biggest Loser: Second Chances included a one-mile foot race in its first week, an event that led to the hospitalization of two of its contestants; Rob Huizenga, the show's medical consultant, when asked about the foot race said that "If we had it to do over, we wouldn’t [have done] it" and noted that in response, the show's producers have "changed a lot of the way [they] do things" (including the close monitoring of contestants’ body temperatures during exercise).^[6]

One attempt to create a more healthy environment after Season 8's dangerous foot race was to include a pool for low-impact cardio. This helped contestants to lose weight in a healthier and safer way than some previous exercise routines on earlier seasons.^[12]

Because the show is a contest that involves eliminations from it, some contestants are encouraged to take risks that endanger their health. Ryan C. Benson, the winner of the program's first season, publicly admitted that "he dropped some of the weight by fasting and dehydrating himself to the point that he was urinating blood". Also since the show Benson has regained all of his weight, but 10–12 lbs.^[6] In 2009, Kai Hibbard (runner-up from the third season) told The New York Times that "she and other contestants would drink as little water as possible in the 24 hours before a weigh-in" and would "work out in as much clothing as possible" when the cameras were off. She further stated that two weeks after the show ended, she had regained about 31 pounds, mostly from staying hydrated.^[6] In a June 2010 interview, Hibbard said, "I do still struggle [with disordered eating]. I do. My husband says I’m still afraid of food... I’m still pretty messed up from the show."^[13]

According to a report by The New York Post, California authorities inquired the show due to allegations of doping contestants. The show dismissed these allegations as false and without merit.^[14] The show is under internal investigation as of July 2018.^[15]

Seasons two and three of The Biggest Loser have been filmed at the Hummingbird Nest Ranch.^[17] The 126-acre (0.51 km²) ranch is an equestrian estate in Simi Valley, California, northwest of Los Angeles.^[18] Recent seasons have been filmed at King Gillette Ranch on Mulholland Highway near Malibu Creek State Park.^[19]

The following table contains records for the American version of The Biggest Loser. Only records which were officially announced on the show are included.

• ^ES notes an extended season
• ^EW notes an extended week

• The Biggest Loser (international editions)