A common question when preparing Paleo meals is do I need to count calories or measure portion size? Most diets require you to measure your food intake in some way, whether that be counting calories or measuring portion size by various methods. Of course the first question usually asked when following any diet is "What can I and can not I eat?". Invariably the second question is "How much can I eat?". Whether you need to count calories on the Paleo diet depends on what your goals are. If you're looking to lose weight then no you do not need to count calories or worry about portion size of Paleo meals. On the other hand if you're an athlete or Crossfitter and switching to the Paleo diet then it's recommended to initially count calories and carbohydrate intake of your Paleo meals to ensure adequate fuel for performance.
Modern day western diets are heavy in grains, cereals, refined sugars and foods that are calorically dense. This means that in a typical western diet there is a lot more energy in food than in the food our Paleolithic ancestors ate. Or put another way, on a typical western diet you only need to eat a smaller volume of food to get the same amount of calories as that of someone consuming Paleo food.
This is because the Paleo diet avoids calorically dense processed foods in favor of whole foods. In particular, vegetables and fruits form the main sources of carbohydrates in Paleo meals, which contain far fewer calories than in starch sources such as rice or pasta, which form a large part of the typical western diet. Processed foods and snacks such as biscuits, crisps, chocolate and ice cream are even more calorically dense.
The result is that if you are trying to lose weight and have switched to a Paleo diet you do not need to count calories, as you are consuming foods which contain significantly fewer calories. If you eat Paleo meals until you are full, and combined with exercise, your body will transition to a natural weight for you. If you are overweight you will lose weight without counting calories.
On the other hand, if you are an athlete or following an intense exercise regime like Crossfit, you need to ensure you are receiving an adequate calorie intake. Crossfitters and athletes switching from a typical diet to Paleo meals often do not consume enough food to keep up an adequate caloric intake. If you eat the same volume of food you will be getting far less energy, which your body needs for your recovery and next workout. In particular, athletes need to ensure they receive enough carbohydrates to fuel their performance, which means consuming a lot more volume of vegetables and fruit compared to starch carbohydrates like rice and pasta. Athletes switching to the Paleo diet should record what food they consume for a week or two to get an understanding of how much they need to eat to reach an adequate calorie intake, and how many vegetables and fruits they require to ensure adequate levels of carbohydrates for performance.