Macros are a tool to help you know how much of what you’re eating. If you have reliable hunger and satiety signals, macros can be very simple. Such as: sub-20 grams of carbs per day, fat and protein in about equal weights to satisfy daily hunger. If you’re just trying to lose weight/fat that will probably do for a while. Although for weight/fat loss it may help to eat less fat and more protein. For many folks this is the ‘forevermore macro’. If it works long term to enable you to maintain weight and health, good for you. If it works for a year or two and then doesn’t, well then yes you can change your macros.
If you don’t have reliable hunger and satiety signals or if you’re eating keto for other reasons than simple weight/fat loss or general health, by which I mean specific medical conditions such as T2D, then to be useful macros may need to be more precise and a bit more complicated. The carb macro should always be sub-20 grams per day and the lower the better. Once you’ve been eating keto for a while it is no problem reducing carbs to sub-15, sub-10 or even zero carbs per day consistently. Protein macros can be based on either lean body mass, if you can measure or calculate it, or total body weight as long as you’re not excessively over or under ‘normal’ weight for your height. The fat macro is generally the difference between the calories from protein subtracted from the total calories required to maintain a steady weight. If you’re trying to build muscle mass, then eat more protein and less fat.
Please do not conclude from the above that I advocate eating to arbitrary numbers . I do not. I advocate eating to numbers determined by trial and error to maintain your weight and body fat %. If you eat keto to resolve a specific medical issue, then eat to numbers determined by trial and error that help alleviate or at least not exacerbate the symptoms of the issue. If you’re trying to increase muscle mass or other lean mass, then you will need to increase protein.
As noted, many folks don’t even bother with macros other than to keep carbs sub 20-grams per day and eat equal amounts of fat and protein by weight (usually guestimated!). The ‘macro’ for them is eat when you’re hungry stop when you’re not. Also, many folks who have lost large amounts of weight say that strictly controlling eating times is just as important or even more so than what exact proportions of fat/protein you eat. Many fast by eating only during a daily ‘window’ of several hours and not eating at all the remainder of the day - and absolutely no snacking . Keep in mind, though, that if you want to encourage your metabolism to eat your endogenous fat, you need to eat less fat off the plate. Daily energy requirements are met by plate fat plus body fat and as long as you give your metabolism sufficient plate fat it will spare your body fat. But you have to do this carefully to avoid slowing down your overall metabolism. For example:
Some folks, like me, do not have significant hunger and satiety ‘signals’ to use them successfully to manage our eating. So we use macros to set daily fat/protein target amounts, not percentages
, and weigh food portions to ensure we do so. Generally, those who do this long term do not find it particularly onerous and I suspect, like me, find it quite interesting to maintain daily logs. Personally, in addition, I do it so I can see exactly what I ate on any particular day and from that determine any interesting outcomes over the next few days.
I think Bikman’s recommendation of 1-2 grams of protein per kilogram of total body weight is the easiest way to calculate macros if you’re not either very large or very small. I’d suggest you start at 1.5 grams and adjust over time as needed. Then by trial and error determine the total energy intake required to maintain stable weight at your new exercise-enhanced level. This may take a few months so be patient. Likely, you will eventually determine a ‘window’ of total intake of +/- 3-400 calories or so within which you will comfortably maintain. (Example: my caloric maintenance window is 2300-2700 calories per day - I’m a moderately active 76 year old male, total weight 145 pounds, BF 14-15%) You will also likely find that you end up with a macro somewhere around 1.5:1 fat grams:protein grams.
PS: About the ‘maintenance window’. If I eat consistently at the upper end of my window, I will eventually (2-3 weeks) start to gain weight. If I eat consistently at the lower end of my window, I will eventually start to lose weight. That’s what I mean by calling it a ‘maintenance window’. I use it, too, for example: if I want to drink some alcoholic beverage I eat at the low end of my window for a few days before and after, since I’m going to get energy/fat from the alcohol and need to allow for that. If I do some IF for a few days, then I’ll eat to the upper end of my window for a few days afterwards to avoid losing weight.