Approach fat loss by focusing on retaining muscle. Why? Gaining and losing fat is significantly easier than building muscle. And as long as you're not in a time crunch, your best course of action is to take as much time as needed so that you can retain all of your muscle while getting lean.
The key is managing your calorie deficit in an intelligent and timely manner, and adjusting training based on your personal goals. If your calories get too low, then it's a matter of basic energy levels falling off, lack of ATP, lack of glycogen, and an overall lack of fuel to function in the gym at a high level. Don't abandon a body recomp process because of short-term strength dips. Put your ego aside and understand you're not going to "feel weaker" forever, and you shouldn't feel that much weaker if you're doing things right in the first place.
So how do you adjust your diet in order to avoid the pitfalls of a lifter who quits after a few weeks? It's simple. You just need some basic math.
Do The Math
- Protein: Have 1 gram per pound of bodyweight
- Fat: 20% of total calories
The rest of your caloric intake should be from carbs. After you figure out how many calories will be coming from protein and fat, simply give carbs the remaining percentage.
Your calorie starting point for the first week of "dieting" is just bodyweight maintenance. Here's the catch: Eat your maintenance level of calories from quality food sources, no junk. Maintenance level is all going to depend on age, activity level, and genetic factors, but a good place to start is bodyweight x 15 per day.
After two weeks, adjust your caloric intake down from your maintenance level, unless you lost weight. If you lost weight there, simply stay there for another week. If you lose weight the second week, then stay there. Your weight loss shouldn't be more than about 1.5 pounds a week.
Once the scale stops moving for a week or two, adjust calories down slightly. So if calories were at bodyweight x 15, adjust to bodyweight x 14 and repeat the process.