Lyle, you might want to read the Zone series of books by Barry Sears. Features of his program include:
- it is oriented towards performance and health rather than weight control. However if one is over-fat, the problem will correct itself
- 40% carbs, 30% fat, 30% protein
- Protein requirement is calculated from your lean body mass (muscle+bone) and your level of activity. Then carbs and fats are adjusted to fit the formula.
- Eat all 3 macronutrients together in a meal, and eat low glycemic index foods to slow the entry of glucose into the bloodstream.
- There is a lot of information about fatty acids in the diet and their impact on health
- There is a high fat variant for endurance athletes. Sears came up with the 40:30:30 for football players and Olympic swimmers. However, Sears acknowledges that endurance athletes might do better with more fat, while maintaining the ratio of carb to protein.
My experience: A few years ago I did Ironman at 190#, with at least 60% of calories from carbs, high glycemic index foods like bananas and Gatorade, and lots of carb loading. In I never lost any weight at all that year, even though by best fighting weight is 175# and I was training 20+ hours per week
Personally, I am going with C:F:P 20:50:30 right now, about 110 g carbs because it is more important at this stage for me to lose fat, and (lucky me) I get ketosis with that fuel mixture. When I get within 15# of my goal, I will likely move towards 40:30:30, and fine tune the ratios at that point. This is just for my martial arts and biking around town. At the moment I have no plans to do triathlons or other endurance events.
Why 40% carbs?
1. I expect it would be difficult to eat and digest >60% fat and protein when there is a high caloric requirement.
2. Full glycogen fuel tank is good, and useful for anaerobic work.
3. IMHO the glucose system is better regulated with insulin than ketones with glucagon. The rapid weight loss in Atkins induction is from glucagon running crazy while its controller, insulin is at low levels. Insulin is a very responsive hormone which can be bad or good depending on your genetics, diet and activity levels.
4. Glucose and ketones are converted to acetyl coenzyme A, then enter Kreb's cycle, where fuel is broken down into energy, CO2 and H2O. I am just guessing here, but there may be more energy available if both fuels are pushing their way into Kreb's cycle instead of just one. That may explain in part why Zone-balanced eating correlates with high performance.
Be warned: in 'Enter the Zone', Sears shows a lack of knowledge about ketosis. He says it is an 'abnormal metabolic state', but later in the book he gives examples of the benefits of high fat diets for fat loss. I did the Zone for a day and tested positive for ketones four hours after the last Zone meal. It is unlikely that he ever tested his athletes for ketones, and they were probably in ketosis part of the time.
I don't know what the best mix is. I just know that it isn't 60:25:15