I’m a personal trainer — here’s the sneaky reason why you’re not losing weight

Working out, eating healthy and still not moving the needle on weight loss? A fitness specialist says there may be a covert reason why.

Experts agree that weight loss happens when the body is in a calorie deficit, meaning you’re expending more calories than you consume.

However, as UK personal trainer and nutritional coach Chloe Thomas explains to the Mirror, that deficit can trigger what’s called “metabolic adaptation.”

“Your metabolism slows down in response to decreased caloric intake,” Thomas told the outlet this week. “This adaptation can make it difficult to keep losing weight or maintain weight loss.”

Thomas maintains that everyone has a “set point.” Influenced by body composition, metabolic rate, genetics and appetite regulation, this marker represents the weight at which the body functions at its most stable, optimal level.

“While your set-point weight can fluctuate slightly in response to changes in lifestyle habits or environmental factors, the body typically defends this weight range through mechanisms that regulate hunger, energy expenditure and fat storage,” Thomas said.

This defense mechanism kicks into high gear when we veer too far from this point, and despite our best efforts, our bodies resist weight loss.

Another reason your pounds are sticking around? Prioritizing cardio over strength training.

Fitness expert and online coach River Hardy tells the Mirror that strength training should be the backbone of any fitness regimen.

“Cardio is a great extra tool to burn some extra calories and send someone into a bigger deficit than what they currently are in with nutrition alone,” Hardy said. “But the most important part of any workout routine is lifting weights.”

While strength training might not immediately burn as many calories as a cardio workout, it builds muscle tissue — which requires more energy and calories over time to maintain.

Hardy’s advice is echoed by Jenna Rizzo, a Georgia-based women’s weight loss coach who recently shared that her No. 1 recommendation for weight loss is strength training.

She explains, “You do not need to waste your precious time doing hours of cardio in the gym. When you strength train, you can focus on specific muscles that you can tone and create shape.”

Science supports the squat. Researchers at Stanford University reported that people who do strength training lose more fat and maintain their blood sugar better than those who do cardio or a combination of strength and cardio.

A separate study, published in the British Journal of Sports Medicine, found that strength training fortifies the muscles as well as the brain. These exercises lower your risk for various medical issues, including cardiovascular disease and diabetes, by improving the brain’s ability to access and process glucose.

Looking to begin? NYC-based fitness coach and personal trainer Claudette Sariya shared the six basic moves you need to conquer.

She recommends everyone master squats, hinges, pushes, pulls, lunges and carries using only their body weight before reaching for the weights.

“Once you feel comfortable with those movements, then you can combine them into more complex moves,” she advised.