Ewunike A. Akpan trains her boot camp class outside.

A class reunion, new outfit, beach vacation or special someone — these are all factors that motivate some people to lose weight, but they’re the wrong reasons, fitness experts say.

If people focus on being healthy and happy, the rest will come, they insist. Going too hard, too soon, can lead not only to burnout and backsliding but, more importantly, injuries.

Intensive workouts like P90X, CrossFit or Insanity can be good ways to jump start a fitness or weight-loss plan, but only with the right start, says Ewunike Akpan, a personal trainer who also runs a boot camp through her company, Lotus Fitness, in Washington, D.C.

“They’re good and safe enough for people to do without being in a gym,” Akpan says, particularly for those who have endurance and already exercise at least 30 minutes five to six days a week. “Everyone should discuss fitness and nutrition goals with a doctor, especially if they are sedentary, rusty or unfamiliar with the moves.”

“It’s not advisable to jump right into a program that has you moving in a completely different way than what you’ve been doing for most of the year,” Akpan explains. “You have to do it in stages.”

Like the announcer warns during a late-night infomercial: “You can’t fake your way through Insanity. You have to work your body to sculpt your body.”

An Energy Boost

“I’ve done some parts of Insanity, but I find it too insane for the pace that I’m comfortable with at this point in life,” says Robin Stone, a longtime health writer who runs a health coaching practice in New York City called HealthJones.

“I’m a big fan of P90X, especially the Ab Ripper, Cardio and Core workouts, because they offer enough variety and challenge to keep me coming back,” she adds. “I did the full P90 several years ago and loved the results. I felt stronger, fitter and firmer, and everything was more defined. I had a lot more energy, too.”

Pianist Marcus Johnson appreciates the extra energy he gets from P90X, as he plays instrumental funk concerts on the road about two weeks each month. He started using P90X in 2010 after seeing photos of himself on the red carpet at the NAACP Image Awards.

“I said I gotta do something,” recalls Johnson, who was 198 pounds at the time.

“In the first 40 days, I lost 25 pounds.” Now weighing in at 175, he likes the flexibility of being able to scale back on the workouts if he’s short on time and to use the system in a hotel room, at home or even in a gym. He says that he takes P90X creator Tony Horton’s mantra to heart: “Do your best, and forget the rest.”

Johnson, who is also CEO and founder of the lifestyle company Flo Wine, is now considering Insanity, following the lead of his chief financial officer who participates in triathlons and Iron Man competitions.

Different Workouts for Different Bodies

P90X, CrossFit, Insanity — Chay Jones has tried them all. “I believe in pushing my body — that’s me,” says Jones, owner of V.FIT DC, a concierge fitness company that customizes programs for individuals or groups wherever they are. “The biggest thing that people have to understand is that everyone is different.” And every workout isn’t suited for every body.

So, what are the differences?

“Get fit, or get out,” says Shaun Thomas aka Shaun T, whose Insanity workout lives up to its name. The ten DVD set is long on hard-core moves and short on rest. That means 60 days of insane jumping and other plyometric moves.

CrossFit – another in the lineup of workout programs — takes a communal approach with thousands of trainers and gyms across the world focusing on high-intensity moves such as weightlifting, rowing, running, rope climbing and pull-ups. Men and women also compete to be the “Fittest on Earth” in the CrossFit Games. It was developed by Greg Glassman in 2000.

“I’m a CrossFit fan and saw great results with it,” says Nichele Hoskins, a fitness instructor and personal trainer in Birmingham, Ala. “With CrossFit, you can do a free workout to see if it’s what you want to do and if the level of intensity is too much.”

Hoskins likes going to the no-frills locations — one in a former auto shop — to commune with other CrossFit devotees.

“I’m just not very good at working out at home,” says Hoskins, whose three dogs get in the way. “I like having an actual community of human beings cheering me on.”

Like Insanity, Power 90 Extreme, or P90X, comes with a series of DVDs and nutrition plan, but for 90 days instead of 60. The workout also offers a greater mix of moves to create “muscle confusion” so that the body has to keep adapting. Billed as the No. 1 extreme fitness program with more than 4 million copies sold globally, P90X includes yoga, stretching, cardio, martial arts, abdomen exercises, calisthenics and jump training, or plyometrics.

“I also added a fun factor to it,” Horton says. “I grew up with coaches who didn’t have a sense of humor. It was always about the win-loss column.”

“I’m trying to get more people in the game,” Horton says. Whether or not they use any of his dozen or so fitness programs, he wants them to share his commitment to exercise every day, even if it’s just for 10 minutes. “It’s as important as brushing my teeth.”

Or, None of the Above

“The muscle confusion is an awesome idea,” says Mark Baugh, a marathoner, trainer and coach in the Washington area. He also likes the infusion of a fun factor into these extreme workouts.

However, Baugh says, “I personally don’t need any of those. I use specific workouts for the types of activities I want to do.” He takes the same approach with many of his clients.

Besides injuries, Baugh says that some people who go too hard too soon end up abandoning their DVD workouts. “Some people max themselves out early, and they store them away and they never use them again. Your body says, ‘Oh hell no — I’m not doing that.’”

Similarly, Baugh adds, a lot of people will walk a mile one week and then jump to five miles the next.

“They’ve taken it out of the fun zone and taken it into the torture zone,” he says.

Instead, Baugh encourages people to find exercises that they enjoy. Exercise can help stimulate dopamine and endorphins, which send feel-good signals to the brain.

“If you keep it in that zone,” he points out, “you’ll look forward to it.”

Yanick Rice Lamb, who specializes in health and social issues, teaches journalism at Howard University. Follow her on Twitter at @yrlamb.