If you want to give ‘low-carb’ a try (20% calories from carbs won’t cause ketosis), substitute the refined carbs (not the good ones such as wholegrains and fruit) for lean proteins (e.g. fish, chicken breast, tofu, legumes) and good fats (avocado, fatty fish, nuts, seeds, evoo).
As long as you follow this as a general guide, I don’t think you can go too wrong. A lot of people do keto/low carb and then use it as an excuse to eat terrible food, because they are ‘fitting within their macros’ - Please don’t be one of them.
P.s. While I have your attention, there’s no good evidence that keto is healthier for your brain or any other organ, unless you’re a diagnosed epileptic.
No dis, but I don’t do macro math. It’s not 3 buckets.
For me now, it’s five food groups and the size/number of portions.
Also ‘eat more of this & eat less of that’ works
 
‘To lose weight, most people need to reduce the number of calories they get from foods and beverages and increase their physical activity.
For a weight loss of 1 to 11⁄2 pounds per week, daily intake should be reduced by 500 to 750 calories.
Eating patterns that contain 1,200 to 1,500 calories each day can help most women lose weight safely, and eating patterns that contain 1,500 to 1,800 calories each day are suitable for most men for weight loss.
In adults who are overweight or obese, if reduction in total calorie intake is achieved, a variety of eating patterns can produce weight loss, particularly in the first 6 months to 2 years; however, more research is needed on the health implications of consuming these eating patterns long-term.’
 
Low carb isn’t necessarily healthier than higher carb, for health rather than carb intake focus on the quality/type of carbs you consume. I’d say a healthy macro split is 45-60 percent carbs, 20-30 percent protein, 25-40 percent fat. Regardless, The most important thing is the source of your macros, a high carb diet of refined grain and pastries will be unhealthy just as a high fat diet of all saturated and trans fat will be unhealthy. Aim for whole minimally/unrefined carb sources like beans, lentils, wholegrains, unprocessed potato and fruit and mainly unsaturated fats such as fish, nuts, eggs, seeds, extra virgin olive oil along with some lean proteins. How you split your macros isn’t particularly important for health along as the source of your macros are good quality wholefoods like the ones previously mentioned. Just aim for a balance of everything and to get enough fiber and essential nutrients and you’ll be pretty healthy regardless of macros.
If your protein, calories, and micronutrients are in the right place, the carb/fat balance you choose is largely irrelevant to general health.
But to directly answer your question–you figure out a calorie target first, then a protein target (1.2-2g/kg is enough to support recovery from exercise, higher is fine if you prefer it). Then you’d set a carb limit (30g, 50g, 100g are common), and fill out the rest of your calories with fat.
Depends what your goals are. Someone who is bodybuilding may end up eating higher percentage of protein if they are trying to consume 150-200g per day.
If you aren’t bodybuilding, it isn’t necessary to have so much protein, and doing so may have some negative effects on various biomarkers, so you’ll be eating more fat.
The percentage of carbs also depends on if you are trying to do an *actual* low-carb diet, trying to reach Ketosis, or if you are just trying to moderate your carb consumption to manage cravings and metabolic health.
Figure out your goals first.