Eating a low carbohydrate and low fat diet is functionally untenable for human beings. We’re adaptable enough to live on a wide variety of food type combinations, but a high protein, low everything else diet does not work out so well. The results have historically been referred to as a condition called “rabbit starvation“.
From Wikipedia – “Rabbit starvation is a form of acute malnutrition caused by excess consumption of any lean meat (like rabbits) coupled with a lack of other sources of nutrients usually in combination with other stressors, such as severe cold or dry environment. Symptoms include diarrhea, headache, fatigue, low blood pressure and heart rate, and a vague discomfort and hunger that can only be satisfied by consumption of fat or carbohydrates.”
I’ve heard of this kind of experience from many people who have tried out the paleo diet. What usually happens is they already come from a diet that is fairly low in fat (because of the damnation of fat by the USDA). Then, upon adopting the paleo diet they switch to eating more lean meats, and try to cut out all the extra junk carbs they ate on a daily basis. With the prevalence of the “caveman” marketing and press for the paleo diet, everybody is imagining that they should eat meat all day long so they really pile on the protein.
All of the sudden, they go from what was probably a 50% / 30% / 20% (carb/protein/fat) ratio of food, to something looking like 30% / 50% / 20% (carb/protein/fat) ratio of food. It’s no wonder they feel hungry all of the time, and generally feel like crap!
The basic idea that needs to be understood here, is that you can be either low carb, or low fat, but not both.
When the USDA ruled that fat was evil, people followed the food pyramid and removed a lot of the fat from their diet. The result was that they had to add a lot of carbohydrates back into their diet, to satiate their hunger. It is difficult to consume that amount of carbohydrates eating just paleo-friendly vegetables and fruit. Either you will have to munch on high fiber broccoli and carrots for 6 hours a day, or eat higher glycemic fruits and starches. It’s certainly not impossible, just look at the Kitavans.
There is an alternative however, and that is to significantly increase the amount of fat in your diet. The paleo community is still divided on the topic of saturated fat, but more and more researchers are discovering that saturated fat may not lead to cardiovascular disease after all. If you want to play it safe, at least add more nuts like walnuts into your diet. Your body will thank you for it.