Medical note first: intermittent fasting isn't right for everyone. Don't try it without talking to your doctor if you have diabetes, take medication, are pregnant or breastfeeding, are under 18 or have a history of disordered eating.
If you're restarting training after a long break and want to try intermittent fasting, the research says it can work as a way to eat less, but it isn't better than normal calorie control, and you need to protect your muscle. Keep workouts short, get enough protein in your eating window and don't change everything at once.
Ready to train? Pick a short workout and start with the reps turned down.
Does intermittent fasting help weight loss?
Not more than other ways of cutting calories. In a 12-week trial of 116 adults with overweight or obesity, a 16:8 group (eating from noon to 8 pm) lost no more weight than a group eating three regular meals. The authors concluded the results did not support time-restricted eating for weight loss.
A 12-month trial of 139 adults with obesity found the same: time-restricted eating plus calorie restriction wasn't more beneficial than calorie restriction alone. Weight loss was 8.0 kg versus 6.3 kg, a difference that wasn't statistically significant.
What about muscle?
That's the concern when you're rebuilding. In the 12-week trial above, appendicular lean mass, the muscle in the arms and legs, was significantly lower in the fasting group. So protect your muscle with regular training and enough protein.
How should you time workouts around fasting?
If you choose to fast, put short workouts close to your eating window:
- Train near the end of your fast or early in your window, so you can eat soon after.
- Keep sessions to 8 to 20 minutes at first.
- Eat a protein-rich meal after training.
- Spread your protein across your meals.
- Skip hard training on days you feel dizzy or drained.
Try this: Pick an AMRAP or EMOM in the app, turn the reps down and finish each round with something in reserve. Skip max-effort Tabata on an empty stomach. See what does Tabata mean and fasted workout after a long break.
The Dietary Guidelines for Americans 2025 to 2030 suggest 1.2 to 1.6 grams of protein per kilogram of body weight a day. Reaching that in a shorter window takes planning. Read how much protein you need to lose fat.
Is it a good idea in your first weeks back?
Often it's simpler not to. You're already changing sleep, training and food. Adding a new eating pattern makes it harder to tell what's working. Build the training habit first, add a modest calorie deficit and decide on fasting later if you still want it. See the 4-week restart plan.
Who should avoid fasting?
Talk to a doctor before fasting if you:
- Have diabetes or take medication for blood sugar or blood pressure.
- Are pregnant or breastfeeding.
- Have a history of eating disorders or disordered eating.
- Are under 18.
- Have a medical condition or take regular medication.
- Get dizzy, faint or irritable when you skip meals.
What are the warning signs?
Stop fasting and get help if you have fainting, a racing heartbeat, severe weakness, confusion or chest pain. If you notice you're obsessing about food or skipping meals when you shouldn't, speak to a doctor or mental health professional.
What should you do if fasting isn't for you?
A simple calorie deficit with regular meals works just as well. Use the NIH Body Weight Planner for a starting estimate, eat protein at every meal and train three times a week. See a weight loss workout plan after a long break and cheat meals and weight loss.
FAQs
Can I work out while intermittent fasting?
Many healthy adults do, with sensible timing and enough protein. Check with your doctor first.
Is it okay to lift fasted?
Light to moderate work is fine for many people. Heavy sessions are better with food on board.
Will intermittent fasting help me lose weight faster?
Trials so far suggest it isn't faster than regular calorie control.
The bottom line
Intermittent fasting is one option, not a requirement. Protect your muscle, get your protein and check with your doctor if you have any health concerns. Then pick a short workout and build the habit first.
Go train, FATBOY.
This article is general information, not medical advice. Train at your own risk. Fasting isn't suitable for everyone. If you have a health condition, take medication or have a history of disordered eating, talk to your doctor or a registered dietitian before fasting or changing your diet.
- intermittent fasting
- nutrition