Muscles don't turn to fat when you stop weight training. They do however, lose mass. Any fat gain you notice will come from eating the same amount you were eating previously, or more, and not exercising to burn calories.
Can muscle turn into fat? A common misconception is that fat will replace muscle if you stop exercising. "It's absolutely not true," says Petty. "Fat cells and muscle cells are different structures and are not interchangeable.
They will become smaller and weaker. If you've been doing high intensity exercise or weight training, you'll find a reduction in your muscular endurance. A detraining period of 12 weeks results in decreased muscle mass and muscular strength, although the muscles can return to pretraining levels.
Some athletes see a loss of about 6% muscle density after three weeks. Some power lifters see losses of as much as 35% after seven months. Young women who trained for seven weeks and gained two pounds of muscle mass, lost nearly all of it after detraining for seven weeks.
Muscle does not “turn into fat.” Period. There is no process in the human body by which muscle – which is made up of mainly protein, amino acids, and water – transforms itself into adipose (fat). The human body, no matter how amazing it can be at times, cannot magically turn one tissue into another.
For most people, strength loss occurs after two to three weeks of inactivity, says Molly Galbraith, a certified strength and conditioning specialist. But it depends on why you take the break. “If you are sick, your body is overstressed, so you'll start to lose strength after two to three weeks,” she says.
This minimal amount of excess weight can make you feel heavier, and your muscles may not respond as well as they normally do because they've had an extra day off, but weight gain in the form of excess fat is still unlikely.
When you stop working out, the body fat increases as your calorie requirement decreases. Your metabolism slows down and the muscles lose their ability to burn as much fat. Also, since you're not burning the same amount of calories as you used to while working out, the extra calories will be stored as fat in the body.
In general, you lose your endurance before your muscles. Your aerobic capacity drops by 5 to 10% after three weeks of no exercises, and after two months of inactivity, you'll definitely find yourself out of shape.
Building muscle is a slow, costly process, and once gained your body doesn't let it disappear so easily. Most studies show that muscle loss doesn't begin until after two or three weeks of complete detraining. That is, no weightlifting or formal exercise of any kind.
Gabriel Lee, the co-founder of Toronto's Fit Squad and a former strength coach, says that generally speaking, muscle mass — i.e. the size of your muscles — starts to dwindle after four to six weeks of inactivity.
If you do less exercise or activity you will become deconditioned. Your muscles weaken and lose bulk including the muscles you need for breathing and the large muscles in your legs and arms. You will become more breathless as you do less activity.
Typically, I recommend that people take a few days off from exercising every six to eight weeks, assuming you work out at a good intensity and are consistent. This gives both your mind and body a chance to recover and adapt to the previous weeks of training.
“However, following long periods of extensive exercise, the body's metabolic system may be stressed to its limit, therefore it is advised for anywhere from a minimum of 3-7 days of complete rest, hydration and sleep.
As for your body, a Skidmore College study found that your metabolism could slow by 4% if you rest for just over a week. That's could be a two-pound gain in a fortnight.
If your muscle atrophy is due to disuse (physiologic), the process can start within two to three weeks of not using your muscles. Neurogenic muscle atrophy may develop sooner depending on your health condition.
According to the research of pro bodybuilder Jeff Nippard, the timeframe to get your muscle gains back is typically around half the time you took off. So, if you had a 2-month break from lifting, it might take just a month to get all of your gains back. Took six months off? You'll need three months to gain it all back.
Past experts have told us that you shouldn't work out after 8 p.m. The National Sleep Foundation advises that you avoid "strenuous workouts in the late evening or right before bed," though it notes that if nighttime workouts don't affect your sleep, there's no need to change your routine.
Regardless of your age, you can reap the benefits of exercise. If you're over 40 and haven't exercised in years (or ever), take heart: It's never too late to start working out. Even those who start exercising in their late 70s can reap the benefits of exercise.
“It's absolutely never too late to start,” Masiello said. “People who begin exercising later in life can't believe how much better they look and feel. Especially when chronic pains they've had for years disappear. Exercise is medicine.”
Bean's point: it's never too late. That said, there are some limits to how much you can progress. "Workouts aren't going to turn someone in their 80s, 90s or 100s into someone who is 40 or 50 years old, but most people can get stronger and improve their endurance," says Dr. Bean.
You're Never Too Old For A Good Physique. It's Never Too Late For Muscle Mass.
After the age of 30, women's bone density and muscle mass starts to decrease if we don't do something about it. This is where 'use it or lose it' really does apply. We experience a decline of approximately 15% per decade after this age (reaching 30% after 70) - affecting our strength, power and endurance.