In my experience, these are the most popular of the diet choices for those looking to lose weight. The idea of low-calorie diets is well known and pretty simple: eat less dietary calories than you burn each day, and the weight will come off.
This is simple logic, and thanks to advanced science, it’s actually very true. As long as you eat less calories than you burn, over time you HAVE to lose weight. Here is why:
We all know that our body burns calories during the day. Technically, a “calorie” is simply a unit of energy. 1 scientific “calorie” is the amount of energy required to heat 1 gram of water 1 degree celsius; 1 dietary “calorie” is the amount of energy required to heat 1 kilogram of water 1 degree celsius. That means that the 5 calorie stick of gum you are eating can bring almost a quarter cup of *ice cold water* to a boil!
The amount of calories you burn a day used to be laboratory tested by heat- how much heat your body gives off is tested (sometimes is pretty strange ways). The amount of calories found in food is tested by burning a sample of the food inside an instrument called a calorimeter- yes, lighting it on fire, basically- and then determining how much the temperature of water inside the instrument changed to determine the amount of energy produced.
The body needs a lot of calories to maintain itself. Some calories are used to maintain the body’s internal temperature- usually around 98.6 degrees F (but for everybody it can be different and still healthy- my usual body temp is 96.8 degrees F). Bringing 8 ounces of ice-cold water to body temp can actually take 70 dietary calories! (1.9 L up 37 degrees).
We get the heat that we need through our food. The body is capable of metabolizing carbohydrates, proteins, lipids, and alcohol to get this energy. The most common chemical equation is for carbohydrates, as this is usually the body’s typical way to get energy:
C6H12O6 (glucose) + O2 -> 6CO2 + 6H20 + ATP (values vary depending on certain steps).
It must be noted that the actual mechanism is much more complicated. The glucose molecule first goes through a process of glycolysis, which turns the molecule into something usable for what is called the Kreb’s cycle (some day I will get into the Kreb’s cycle and complete metabolism of the various macronutrients- but today is not that day).
In the end, this ATP is what allows “energy” to be transferred. ATP is needed for active transport within cells (to help maintain proper concentrations in the cells, to keep you from dying) and it is also a crucial requirement in muscle contraction (will go over this mechanism later as well).
Put simply: we use the food we eat to make ATP, the body’s “energy” molecule (kind of like money, actually). To make ATP, molecules of a substance we can metabolize must be present in a cell. Typically, this is glucose that enters the cell from diffusion- and after we eat, the carbs we just ate turn into glucose into the blood stream first. Our cells pick up this glucose no matter what
Now, our bodies like to maintain a certain level of glucose in the blood stream. When there is too much glucose (as in, after a big meal), certain receptors can tell, and they release chemical signals to control hormones. This stimulates the liver and muscles to take up the glucose in the blood stream and store it as glycogen- a form of carb that is easier to convert from and to than fat- and once those stores are “full”, the extra glucose is stored as fat (ultimately, this is what happens to *all* metabolized foods). The reverse is also true- when the blood sugar level is too low, the brain stimulates the body to release glycogen and fat (depending actually on how quickly the glucose levels are depleting!)
Thus, what happens when you enter a low-calorie diet is that your food cannot sustain your activities, your blood sugar drops slightly, and to maintain a proper level of blood glucose, your body releases some of its fat and glycogen stores (ultimately using fat to fuel the body despite a calorie deficit)
- A LCD can be *very* effective if done correctly. Because there are some processes the body cannot shut off and energy MUST be burned the body will take the needed extra energy through its own storage, decreasing body weight.
- A LCD does not require any restriction of food groups. This is incredibly desirable for some people who like the idea of still being able to eat ice cream every now and then, or those without access to a lot of fresh food, such as those living in small, secluded towns.
- LCDs are usually easy to follow; all pre-packaged food items are required by law to state the calories and calorie information is readily available. Likewise, most formulas for estimating BMRs are fairly accurate and easily found, while testing your own RMR is now very simple (a 15 minute breath test).
- A calorie deficit is quite literally the only way to ensure weight loss without changing body chemistry.
- Lowering of the BMR. When the body realizes it is constantly getting less than adequate calories, it will “turn off” certain functions it doesn’t think are as necessary.
- Can be difficult to maintain. In today’s age, 4,000 Calories/day seems commonplace to many. Most restaurant food and street fare are high in calories and are often difficult to avoid, and you may feel very hungry.
- Can lead to muscle loss. While any weight loss will inevitably be both from fat and muscle, LCDs tend to produce more muscle loss than exercising.
- Can lead to eating disorders. The emphasis on calories can lead people to think of calories and thus food as the “enemy” and can be the start of eating disorders in some.
- Is typically not rapid on it’s own. If calories are cut to 1200/day, a person my height and weight could only expect to lose about a pound a week. This is sometimes not a rapid enough weight loss for some people.
- Damages to the heart (alternatively). There have been some studies to suggest that rapid weight loss (occurs if somebody misinformed cuts calories too much) stresses the heart.
- Allows unhealthy foods. Unless accompanied by some other diet rules, a LCD itself will only have somebody losing weight, but they might not necessarily be healthy-
- Nutritional deficits. If not monitoring carefully, people on LCDs might develop problems that come from inadequate vitamins and minerals- hypokalemia (low potassium), beri beri, and especially anemia can result. Even if the body is not down to the levels to be diagnosed with nutritional diseases, undesired side effects can occur (such as hair loss, easy fatigue, skin problems, and slow healing).
For many people, low-calorie diets work very well, but one must take precaution to avoid the nutritional problems that come from eating little. Those on LCDs should partake in some physical activity if possible, and nobody should go lower than 1200/day without talking to their doctor. While 1200 is not a “magic number,” I enforce it because rapid weight loss (especially rapid weight loss without muscle training) can lead to serious problems, it is VERY hard to get all the nutrition you need from the foods you eat on a LCD, and the risk of setting yourself up for an ED is NOT okay with me (it was how my problems started). If you think 1200 is too much for you, there is NO REASON not to get doctor clearance. He or she may even be able to prescribe supplementation for you at a cheaper cost than you would pay at a health store.