“The concept that “a calorie is a calorie” underlies most conventional weight loss strategies. According to this principle, obesity results from an imbalance between energy intake and expenditures. The proposed cure is to eat less and exercise more. However calorie restricted, low fat diets have poor long-term effectiveness in the outpatient setting. In a sense, these diets may constitute symptomatic treatment that does not address the physiologic drives to overeat. From a hormonal standpoint, all calories are not alike.”
David Ludwig, M.D.[i] 
Why All Calories are NOT Created Equal
In the last chapter you learned that calorie restriction doesn’t work. That’s the reason most diets fail. Dropping extra pounds is not a simple matter of eating less. In fact, if you eat too little you set off a chain of molecular events inside your body that will actually cause you to gain weight.
Nonetheless, our culture tries to convince us that if we consume fewer calories we will lose weight. But this doesn’t tell the full story. Calories are important. But it isn’t the amount of calories so much as the type of calories you consume that makes a difference in terms of how much you weigh and how healthy you are. But before we explore that, let’s have a closer look at what calories are and what they do.
What are Calories and Where do They Come From?
So what is a calorie anyway? A calorie is a simple unit of energy. It is defined  as  the  quantity  of  energy required  to  raise  the  temperature  of  1 gram  of  water  by  1 degree  centigrade  at  atmospheric  pressure .
We get calories from the food we eat. We consume food, and the chemical processes that make up our metabolism break up this food and turn it into energy. Burning this energy created by our metabolic machine allows us to do everything from breathing to running marathons.
It’s sort of like putting fuel into a car. You have to put the fuel in to make the car run. This is exactly the case with people and food. Food is our fuel. We consume calories so that we have something to burn. It is these fuel-calories that make us run.
We need a certain amount of caloric intake just to keep the basic functions of our body operating. And then we need some additional calories to do things like get out bed in the morning or go for a run. You learned about all this in the last chapter.
A few hundred years ago Isaac Newton proved that all energy in the universe is conserved—this is known as the first law of thermodynamics. Applied to your weight and what you know about caloric intake, this law suggests that if you eat the same number of calories you burn, you will stay the same weight. If you eat more calories than you burn, you will gain weight; if you eat less than you burn, you will lose weight. This seems perfectly logical. The problem? It’s not true.
Why All Calories are NOT Created Equal: A Lesson From Physics
I certainly wouldn’t presume to throw out Isaac Newton’s laws. But how they apply to the calories you eat is not as simple as the first law of thermodynamics suggests.
Let’s examine a similar physics-oriented example that you probably remember from high school. Take one pound of feathers and one pound of lead and drop them in a vacuum. Which drops faster? Those of you who answered, “lead” need a refresher course in physics.
In a vacuum they both drop at the same rate. They are the same weight — one pound – they have the same mass, so they drop at the same rate. Now take that same pound of feathers and pound of lead and drop them off the George Washington Bridge in New York City. Which drops faster? If you answered “lead” this time, congratulations.
Why? Air resistance. You can’t see it, you can’t taste it, and you can’t smell it. But air resistance is real and it affects how lead and feathers move through it. Even though the lead and feathers in this example have the same weight/mass, they have different properties that cause them to move through air differently.
Calories behave in the same way. When calories are burned in a laboratory, they are all created equal and release the same amount of energy. There is no difference between a thousand calories of kidney beans, or a thousand calories of a low fat muffin or cola — until they are metabolized.
Your body’s metabolism is like the air resistance in the example above. The calories you eat are absorbed at different rates, have different amounts of fiber, carbohydrates, protein, fat, and nutrients – all of which translate into different complex metabolic signals that control your weight. You may not be able to see, taste, or smell your metabolism anymore than you can see air resistance, but it has an impact on how calories are consumed in your body just the same.
For example, all the sugar from a soda enters your blood very rapidly, while the same amount of sugar from kidney beans enters your blood slowly and some of it may not even be absorbed because of the high fiber content in the beans. If you drink a soda and all the sugar in it goes into your bloodstream at once, the calories you aren’t using at that moment will be stored as fat. On the other hand, if you eat the kidney beans and the sugar in them is absorbed over time, your body has a greater chance to make use of those calories. That means more of them will be burned and less will be stored. Also because of the high fiber content of the beans, not all the calories will be absorbed.
Pull Quote: Food that enters your blood stream quickly promotes weight gain; food that enters slowly promotes weight loss.
Recent studies have turned this idea that all calories are created equal on its head. Studies show that high carb diets comprised of rapidly absorbed sugars can increase blood sugar and insulin levels, causing weight gain, as well as increase cholesterol and triglycerides that lead to a fatty liver, in turn causing even more weight gain. So rapidly absorbed glucose or sugars increase both sugars and fats in the blood and liver, doubling your problems.
In a recent study, leading nutrition researchers, including Walter Willett, M.D., and his group from the Harvard School of Public Health[ii]  designed a study to determine whether low-fat or low-carbohydrate diets were better for losing weight.
The results were startling. The researchers fed their group of overweight patients three different diets all carefully controlled and prepared for them daily in a Boston restaurant for 12 weeks. The first group ate a low-fat diet of 1,500 calories (55% carbohydrate, 30% fat, 15% protein) for the women and 1,800 calories for the men. The second group ate the exact same number of calories but from a low-carbohydrate diet (5% carbohydrate, 30% protein, 65% fat). The third group also consumed a low-carbohydrate diet, but they ate 300 more calories a day than the other group: 1,800 for women and 2,100 for men.
The researchers discovered that the low-carb group eating the same number of calories as the low-fat group actually lost more weight. The low-carb group lost an average of 23 pounds compared to 17 pounds for the low-fat group despite eating exactly the same number of calories. That’s 6 pounds more in 12 weeks. While the study was only 12 weeks, the findings are worth noting.
The real question is, what type of carbs and fats were used. The “low carb” diet was predominately a diet of whole unprocessed foods – lean animal protein, vegetables, whole grains, and beans – in other words a basic Mediterranean style diet. The low fat group ate foods that were higher in refined carbohydrates. But as we are learning here, the low carb movement will also go by the “weigh-side”.
But what was even more startling was that the group eating 300 more calories a day with the low-carb diet lost more weight than those eating the low-fat diet, even though the 25,000 more calories they ate should have amounted to seven pounds of increased weight. They actually lost an average of 20 pounds or 3 pounds per person more than the low-fat group, who ate 25,000 less calories during the 12 weeks.
One final study drives the point home. Harvard professor, Dr. David Ludwig studied three groups of overweight children,[iii]  feeding each group a breakfast containing the identical number of calories. One group ate instant oatmeal; one group steel-cut oats (the type that takes about 45 minutes to cook) and the third group had a vegetable omelet and fruit.
Their blood was measured before they ate and every 30 minutes after for the next five hours. Then they ate a lunch identical to the meal they ate for breakfast. After finishing lunch, they were told to eat whenever they were very hungry for the rest of the afternoon. What happened was startling.
Many of you would think that the healthiest breakfast would be the oatmeal. But it was actually the omelet. The group that ate the instant oatmeal (the breakfast that entered the blood stream and turned to sugar the fastest) ate 81% more food in the afternoon than the group that had the omelet. Not only were they hungrier, but also their blood tests looked entirely different. The instant oatmeal group had higher levels of insulin, blood sugar, blood fats and adrenalin even though they ate the same calories as the omelet group. Though the steel cut oats were better than the refined oats, the children who ate the steel cut oats still ate 51% more food than the children who ate the omelet.
The conclusion here is that the kinds of calories you consume have a big impact on how much fat you gain, because different types of food are metabolized in different ways.
But what’s even more interesting is the fact that the calories themselves actually have an affect on how your metabolism functions. The type of food you eat has a big impact on what your genes tell your metabolism to do. This means that the types of calories you consume have a dual impact on the way you metabolize food. They both act as a source of energy AND a source of information or instructions to your genes that control metabolism.