A lot of dietary guidelines are framed in terms of percentages (i.e. ADA says eat 55/25/15 CHO/FAT/PRO, Zone says 40/30/30, etc.) Sometimes people say “if you eat X percent of your calories from protein, you risk straining your kidneys” or “if you eat Y percent of your calories from fat, you risk atherosclerosis”. It seems like those sorts of risks would emerge from eating too much fat or protein, not as a percentage of your diet, but in absolute terms (i.e. more than 15 grams of saturated fat a day, or something like that). If you eat fewer calories, it seems like you can stay below these thresholds more easily (in addition to reducing your need for bolus insulin) and have more flexibility in terms of percentages.
What do we think about this? There’s a lot of evidence that moderate calorie restriction promotes weight loss, reduces risk of heart disease, and is generally good for you, but this is somewhat controversial. If we can restrict calories, do we need to worry so much about macronutrient breakdowns, within reason? I ask partially because the calorie guidelines promoted by the ADA sometimes seem absurd (like I’m 6’7" and a very healthy 200 pounds, but I don’t need to eat 3200 calories a day; someone who was 5’10 and 150 pounds might need 2400, though).