In order to burn fat and build muscle [1], you're going to need to be very diligent with your training routine and nutrition. While you won't need to do any extreme diets like the keto diet [2], you will need to pay attention to what you're putting into your body and when. If you're consistent with these two things, you should begin to notice a transformation in your body by eight weeks.
Eat More Protein
Whether you're trying to maintain your weight, lose weight, or gain weight, you need to be getting in an adequate amount of protein. Eating foods high in protein [4] is great for losing weight because it keeps you full longer and your body burns calories digesting it. I typically use this guide [5] to help clients figure out how much protein they need to have at each meal.
Get More Sleep
Don't let your workouts and diet go to waste by forgetting to sleep. If possible, try to get eight hours of sleep. Sleep is crucial because this is when the hormones that aide in muscle growth — testosterone and growth hormone — are released.
Lift Heavy and Lift Often
Doing one strength-training session a week isn't going to cut it. If you're a beginner, try to get in three strength sessions a week. If you're more advanced, aim for four to five sessions. Don't forget that if you want to build muscle, you're going to need to put your muscles under tension with heavy weight. As always, choose a weight that will challenge [6] you without jeopardizing your form.
Start Sprinting
If you want to build muscle and get lean [7] fast, start sprinting. Sprinting will not only allow you to get faster, but your muscles will become stronger and more defined because it's an explosive style of training.
Up the Intensity
One of the biggest mistakes I see people unknowingly make is not training hard enough. No, you don't need to grunt and growl during your workouts, but you need to be going hard. This means taking less breaks to go on Instagram, choosing heavy weights, and working your ass off!
Eat Less Carbs on the Days You're Inactive
To prevent a weight-loss plateau [8], eat less carbs on the days when you're inactive. Eating carbs is important for recovery and energy [9], but if you eat too many calories, you can actually end up gaining body fat [10]. Eat less fruit on this day, don't have protein shakes, eat lots of lean proteins with green veggies, and eat healthy fats.