6 Brain Fuel RulesThe brain uses more energy by size than any other part of the body. When it comes to the brain and body, a calorie is not a calorie. The sources of those calories matter. It is ridiculous that poorly educated dieticians and doctors still spew horribly damaging food advice to patients. Your brain deserves so much more.A calorie is a calorie IS a calorie, they say that it doesnt matter whether you eat a 100 calories of candy or broccoli, they will have the same effect on you.When burned in the lab all calories have the same 4184 Joules of energy. But the human body is a highly complex biochemical system with elaborate processes that regulate energy balance.Different foods use different biochemical pathways. Food have a major effect on the hormones and brain centers that control hunger and eating behavior. The foods we eat can have a huge impact on the biological processes that govern when, what and how much we eat. Some foods will have almost immediate short lived effect on the brain while others provide stable lasting energy for focused thoughts. Here are a few examples:1. Fructose vs GlucoseThe two main simple sugars in the diet are glucose and fructose.These two seem almost identical. They have the same chemical formula and weigh the exact same.But to your body, the two are completely different.Glucose can be metabolized by all of the bodys tissues, but fructose can only be metabolized by the liver in any significant amount.Here are a few examples of why glucose calories are NOT the same as fructose calories:Ghrelin is the hunger hormone. It goes up when were hungry and down after weve eaten. One study shows that fructose leads to higher ghrelin levels (more hunger) than glucose.Fructose does not stimulate the satiety centers in the brain in the same way as glucose, leading to reduced satiety.A high consumption of fructose can cause insulin resistance, abdominal fat gain, increased triglycerides, blood sugar and small, dense LDL compared to the exact same number of calories from glucose.Keep in mind that this applies to fructose from added sugars only, not the fructose from fruit. Fruits also have fiber, water and significant chewing resistance, which mitigate the negative effects of the fructose.Bottom Line: Same number of calories, vastly different effects on hunger, hormones and metabolic health. Because a calorie is not a calorie.2. The Thermic Effect of FoodDifferent foods go through different metabolic pathways.Some of these pathways use more energy to process the same number of calories than others.The more efficient a metabolic pathway is, the more of the food energy is used for work and less is dissipated as heat.The metabolic pathways for protein are less efficient than the metabolic pathways for carbs and fat.Protein contains 4 calories per gram, but a large part of the protein calories are lost as heat when it is metabolized by the body.The thermic effect of food is a measure of how much different foods increase energy expenditure, due to the energy required to digest, absorb and metabolize the nutrients.This is the thermic effect of different macronutrients (7):Fat: 2-3%.Carbs: 6-8%.Protein: 25-30%.100 calories of protein would end up as 75 calories after heat loss to digest it, while a 100 calories of fat would end up as 98 calories.There is also one study that compared two sandwich meals that had the same number of calories and macronutrients. However, one sandwich was made with whole grains and cheddar cheese, while the other was made with refined grains and processed cheese. Those who ate the whole grain sandwich burned twice as many calories digesting the meal.Bottom Line: Protein calories are less fattening than calories from carbs and fat, because protein takes more energy to metabolize. Whole foods also require more energy to digest than processed foods.3. Protein Kills Appetite and Makes You Eat Fewer CaloriesThe protein story doesnt end with increased metabolism.It also leads to significantly reduced appetite, making you eat less calories automatically.The studies show that protein is the most fulfilling macronutrient, by far (12, 13).If people increase their protein intake, they start losing weight without counting calories or controlling portions. Protein puts fat loss on autopilot (14, 15).In one study, those who increased their protein intake to 30% of calories automatically started eating 441 fewer calories per day and lost 4.9 kg (11 lbs) in 12 weeks (16).If you dont want to go on a diet but simply tip the metabolic scales in your favor, then adding more protein to your diet may be the simplest (and most delicious) way to cause automatic weight loss.It is very clear that when it comes to metabolism and appetite regulation, a protein calorie is NOT the same as a carb calorie or a fat calorie.Bottom Line: Increased protein can lead to drastically reduced appetite and cause automatic weight loss without the need for calorie counting or portion control.4. The Satiety Index Different foods have different effects on satiety.It is also much easier to overeat on some foods than others.For example, it may be quite easy to eat 500 calories (or more) of ice cream, while youd have to force feed yourself to eat 500 calories of eggs or broccoli.This is a key example of how the food choices you make can have a huge impact on the total calories you end up consuming.There are many factors that determine the satiety value of different foods, which is measured on a scale called the satiety index (17).The satiety index is a measure of the ability of foods to reduce hunger, increase feelings of fullness and reduce energy intake for the next few hours.If you eat foods that are low on the satiety index, then you will be hungrier and end up eating more. If you choose foods that are high on the satiety index, you will end up eating less and losing weight.Some examples of foods with a high satiety index are boiled potatoes, beef, eggs, beans and fruits, while foods that are low on the satiety index include donuts and cake.Clearly whether you choose fulfilling foods or not will have a major difference on energy balance over the long term. Because a calorie from a boiled potato is not the same as a calorie from a doughnut.Bottom Line: Different foods have different effects on satiety and how many calories we end up consuming in subsequent meals. This is measured on a scale called the Satiety Index.5. Low-Carb Diets Lead to Automatic Calorie RestrictionSince the year 2002, over 20 randomized controlled trials have compared low-carb and low-fat diets. The studies consistently show that low-carb diets lead to more weight loss, often 2-3 times as much.One of the main reasons for this is that low-carb diets lead to drastically reduced appetite. People start eating less calories without trying (18, 19).But even when calories are matched between groups, the low-carb groups usually lose more weight, although it doesnt always reach statistical significance (20, 21, 22).The biggest reason for this is probably that low-carb diets also cause significant water loss. Excess bloat tends to go away in the first week or two (23).Another reason is that low-carb diets tend to include more protein than low-fat diets. Protein takes energy to metabolize and the body expends energy turning protein into glucose (24).Bottom Line: Low-carb diets consistently lead to more weight loss than low-fat diets, even when calories are matched between groups.6. The Glycemic Index There are many controversies in nutrition and the experts dont agree on many things.But one of the few things that almost everyoneagrees on is that refined carbs are bad.This includes added sugars like sucrose and high fructose corn syrup, as well as refined grain products like white bread.Refined carbohydrates tend to be low in fiber and they get digested and absorbed quickly, leading to rapid spikes in blood sugar. They have a high glycemic index (GI), which is a measure of how quickly foods raise blood sugar.When we eat a food that spikes blood sugar fast, it tends to lead to a crash in blood sugar a few hours later also known as the blood sugar roller coaster. When blood sugar crashes, we get cravings for another high-carb snack.In a study that served people milkshakes who were identical in every respect except that one had high GI carbs while the other had low GI carbs, the high GI milkshake caused increased hunger and cravings compared to the low GI shake (25).Another study found that teenage boys ate 81% more calories during a high GI meal compared to a low GI meal (26).So the speed at which carb calories hit the system can have a dramatic effect on their potential to cause overeating and weight gain.If youre on high-carb diet, it is crucial to choose whole, unprocessed carb sources that contain fiber. The fiber can reduce the rate at which the glucose enters your system (27, 28).The studies consistently show that people who eat the most high glycemic index foods are at the greatest risk of becoming obese and diabetic. Because not all carb calories are created equal (29, 30).