Does fasting burn fat or muscle first?

Fasting prioritizes burning glycogen (stored sugar) over body fat; some muscle protein is converted to glucose, but muscle tissue is generally preserved unless the fast is prolonged (several days) or body fat percentage is extremely low ( 31 ).

Who should avoid fasted cardio?

Individuals with a history of hypoglycemia, pregnant women, those with eating disorders, and high-performance athletes requiring maximum glycogen availability for competition should avoid fasted cardio.

Is it okay to lift weights while fasting?

Yes, it is okay to lift weights while fasting ( 32 ). Focusing on moderate reps and staying hydrated are key to safety and performance. However, some people find they don’t see the gains or performance improvements they aim for when lifting weights without adequate fuel.

What should I not do after fasting?

You should not break your fast with highly processed, sugary foods or a massive binge meal, as this can cause a rapid insulin spike and digestive distress ( 27 ). Aim for a balanced meal of easily digestible, nutrient-dense foods.