Why women over 40 should never diet and exercise at the same time

Doing both could have serious consequences for your health!

Why you should never diet and exercise at the same time: woman running up stairs
(Image credit: Getty Images / Corey Jenkins)

We all know the age-old weight loss adage “move more, eat less”, but now, it seems, it may not be the best advice – especially if you’re over 40.

Always thought that if you diet and exercise at the same time, you'll lose more weight? Sadly, you’re wrong. In fact, you could be doing more harm than good. So it could be time to ditch the best fitness tracker for a while. That’s because a study has revealed that just a 30% drop in calories (which is equivalent to 1,400 calories per day for women), combined with exercise, could lead to bone density loss.

The study was conducted by researchers at the University of North Carolina. Scientists compared the effects on mice that were fed a standard diet and those with a diet with 30% less calories than normal.

The results showed that although exercise increased bone mass on mice fed a normal diet, it actually had the opposite effect on mice fed the fewer calories.

If you were to drop calories even further, the effects on bone health would be even more detrimental. Here’s what you need to know:

Why you should never diet and exercise at the same time

So, why is diet and exercise at the same time so bad for bone health? “We all know that exercise increases bone mass and reduces bone fat. And excess calories tend to increase fat in the bones, leading to osteoporosis,” says nutritionist Georgios Tzenichristos, director of London’s LipoTherapeia aesthetic practice. “So, one would expect that combining exercise and diet should lead to even better bone health. Yet, this study shows the opposite.”

And the reason why? “The secret lies in bone energy reserves,” reveals Georgios.

“When we diet, we tend to accumulate fatty acids in the bone marrow. This is to serve the local energy needs in the bone. This study has shown that fatty acid absorption inside the bone has increased by 4,088% on the diet mice. By adding exercise into the mix, those emergency energy reserves were depleted. This leave bone cells starving and unable to repair and build bone mass.”

What makes this especially bad for women over 40?

If you’re a woman over 40, the risk regarding bone health is higher, as bone quality starts to naturally decline, thanks to the menopause.

It’s not just bones that are affected, either. In fact, low-calorie diets and exercise are also bad for the skin. “The body does not have enough nutrients to repair both muscles and skin with the reduced food intake and the increased tissue breakdown due to exercise,” says Georgios.

READ MORE: Study reveals why a plant based diet could negatively impact brain health

Instead, the best way to lose weight is to first diet for a few weeks, combined with only mild exercise,such as walking. Then, gradually ease off the diet and increase your exercise intensity and duration.

“In this way, you lose the bulk of the weight with a strict – but never extreme – diet, and then you maintain it with exercise and healthy eating,” says Georgios.

Lucy Gornall is the former Health & Fitness editor at Future and a personal trainer specializing in pre and post-natal exercise.