A trainer who has worked with Meghan Markle and Jennifer Aniston shares his top tips for boosting longevity

• Building muscle can help boost your longevity and fitness, said celeb trainer Sebastian Lagree.
• With star clients like Meghan Markle, he said low-impact strength training is 'the future of fitness.'

If you want to live a long, healthy life, you need to start doing strength workouts, according to a celebrity trainer.

Resistance training, particularly with low-impact exercise, is key to healthy aging, says Sebastien Lagree, the founder of Lagree Fitness who has worked with A-listers like Meghan Markel, Sophia Vergara, and Jennifer Aniston.

"Not enough people understand the benefits of resistance training. It's not just for the aesthetics," he told Business Insider. "Now that I'm 50, I've started to spend a lot more time on how to make these workouts the best for longevity. It's not a consideration, it's a necessity."

But working out is just the beginning. Lagree said his approach for clients as well as his own personal routine focuses on muscular strength, consistent habits, and heart health, as well as simple nutrition tips to improve your fitness for the long haul, both in and out of the gym.

Focus on building muscle to keep your body and metabolism strong

Resistance training to build muscle and strength is a key part of adding healthy years to your life, Lagree said (and there's plenty of research to back it up).

Lagree Fitness classes use unique equipment that incorporates springs for resistance instead of traditional weights, which he said can be easier on the joints than activities like HIIT. The workouts also focus on a "time under tension" strategy to help build muscular endurance, core strength, and balance, all of which can help make you more durable and resilient as you age.

"I've been preaching low-impact workouts as the future of fitness. With the low impact comes longevity, you can't expect to do high impact forever and expect it to be good for your joints," he said.

Lagree said he loves to hit the gym himself for bodybuilding workouts, and a major perk of building muscle is that it can increase the amount of calories you burn, helping you to better use the food you eat for energy.

"When you bodybuild, nutrients in your body become a source of fuel for your body," he said.

Regular strength training workouts allow him to make the most of having a sweet tooth, tapping into all those carbs for better gains.

"It helps tremendously to put on some muscle," he said.

Go on daily walks to stay fit without a gym

Beyond regular workouts, adding more movement to your day is a great way to boost your health and fitness, especially if you're a beginner, Lagree said.

He enjoys outdoor activities like hiking, but even walking each day can help improve your heart health, which plays an important role in longevity.

A major bonus of walking is that you don't need a gym membership or any equipment, so you're more likely to actually do it, he added.

"If part of your fitness plan is to go to a gym 30 minutes away, that's not a good plan because eventually that trip is going to get old," Lagree said. "Motivation comes by doing, not just by wishing."

Find a workout buddy to keep you exercising

Lagree said inviting friends to exercise is part of his routine whether he's in his home gym or on the road.

"I very rarely work out by myself even though I've been doing it for more than 30 years," he said.

Joining a supportive community is one of the best ways to stick to a workout plan, according to a Harvard researcher.

Recent research on some of the longest living people in the world, in areas known as Blue Zones, also finds that community, and social exercise, are crucial. A group of friends can make fitness feel like a fun social activity, instead of a chore, staves off gymtimidation, and provides support and accountability in keeping consistent with your workouts.

Enjoy yourself in moderation

But exercise is just one part of the longevity equation, and research suggests what your diet can help extend your lifespan too.

Lagree said as someone who loves food, his approach has always been to focus on portion sizes, not cutting out foods entirely.

"I'm always traveling, there are always huge hotel buffets, and I love to eat," he said. "I'm French, I love pastries, so everywhere I go, I've got to try a chocolate croissant because it might be the best one. I just eat less."

Lagree said it's also important to be realistic about your goals and expectations, and plan ahead to avoid setting yourself up for failure later on.

"People think 'Whatever I gain, I'll lose it by working out twice as hard.' I do the same thing!" he said. "It's the same mistake we make on the weekends. We have this way of talking ourselves into eating more, thinking we'll burn it off tomorrow, we never will."

Instead, focus on being consistent over time — healthy habits can take a few weeks to build at first, Lagree said, but over time add up to help you stay strong and healthy long-term.