Loaded question Trudy – but a good one. Of course I need to state my disclaimer here & tell you that I am not an RD or a physician & my opinion is for educational purposes only & not to be construed as medical advice. Ok, now that that’s out of the way, here’s my answer. As a general guideline, I typically go with 40 – 50 % Carb, 25 – 30 % protein & 25 – 30 % fat – assuming it’s a healthy adult with no medical issues. However, each person has their own needs – whether it’s for medical reasons or other reasons. For instance, strength athletes need more protein. Diabetics should probably stay on the lower end of carb intake. These percentages have worked well for me over the years, but as I said, everybody is different & has specific needs.
I never give clients specific breakdowns to follow, but when asked my “opinion,” that’s what I say. As far as weight loss goes (which is your real question), it’s simply a matter of them consuming the right amount of calories & hanging close to the appropriate percentages of nutrients. If they need to lose weight, they have to consume less calories than they’re expending – plain & simple. I was always big on trying to calculate one’s total energy expenditure & work it from there – typically go with a 500 calorie/day deficit. As I said, it’s worked well over the years. It’s not an exact science, but people need some sort of guidelines to succeed. With obesity rates as they are, not much is working, is it?