Efficient Dieting: Formula & Energy Transfer

Instructor: Stephanie Gorski

Steph has a PhD in Entomology and teaches college biology and ecology.

Are you trying to gain or lose weight? In this lesson, we will discuss a simple formula to estimate how many calories you expend in a day. We'll also talk about a few dietary factors that contribute to weight gain or loss.


Do you know anyone with a pet lizard, or maybe a scorpion or tarantula? Have you ever noticed how little they eat? Tarantulas can go for months without eating! But you certainly can't. Why can a tarantula go on such a hardcore diet, but a human can't? And why do you hardly ever see a fat tarantula?

The answer has to do with metabolism. Metabolism is the biochemical processes that occur within your cells that help your cells to maintain life. You burn more Calories than a scorpion or tarantula because you're warm-blooded, and it takes a lot of energy to keep your body hot.

Sometimes people like to blame their weight loss failures on ''slow metabolism''. But, with the exception of a few endocrine problems like hypothyroidism, most of the time your metabolism isn't the problem. Sometimes people selling diet advice will claim that certain kinds of food, or eating at certain times of day, will speed up your metabolism. But the reality is that your metabolism doesn't change much at all. The few exceptions to this rule don't really make effective diet strategies, either. For example, you can speed up your metabolism by having a bit of coffee. But if you have coffee every day, your body will build up a tolerance to it, and it will no longer speed up your metabolism.

That said, having a lot of muscle mass does boost your metabolism and can make weight loss easier.

Calories In, Calories Out

You might have heard the mantra ''Calories in, Calories out'' from dieticians or fitness fans.

''Calories in, Calories out'' means that weight gain and loss are simple chemical processes that take place within your body. You can't possibly gain weight if you eat fewer Calories than you burn. You can't possibly lose weight if you eat more Calories than you burn. This is the first rule of weight gain/loss, and it's absolutely true.

But if you've ever tried to gain or lose weight, you know that real life is a bit messier. How many Calories you take in, and how many Calories you burn, have a lot to do with how hungry you feel, your physical and emotional state, and how food is presented.

Technically you could lose weight just eating cupcakes, but it would be hard not to eat too many cupcakes!
Technically you could lose weight just eating cupcakes, but it would be hard not to eat too many cupcakes!

Is a Calorie Just a Calorie?

When people are fed measured diets in laboratories, the percentage of carbs, fats, and proteins don't affect how much weight they gain or lose. However, in less-controlled environments, carbs, fats, and proteins do matter. Fats have 9 Calories per gram, while carbs and proteins have only 4 Calories per gram. So if you eat an equal portion of a high-fat food vs. a high-protein food, you will have eaten more Calories with the high-fat choice. Therefore, you will likely feel fuller on the same number of Calories if you eat a high-protein diet than a high-fat diet.

Some short-term studies have shown that a high-protein diet can help with weight loss, although long-term studies are less optimistic.

So what about carbohydrates? Highly processed grains and sugary foods are high-carb, but so are whole wheat, fruits, and vegetables. Processed grains and sugary foods are easy for your body to break down quickly. Therefore, your blood sugar spikes and then plummets after you eat these foods. Whole grains, fruits, and vegetables take more time for you to digest. The effect on your blood sugar is much more subtle, which makes you less likely to binge eat.

Consider what you drink. If you drink a soda, you'll consume a lot of Calories in the form of carbohydrates. But you probably won't get any less hungry. This is why sodas are considered high-risk for weight gain. Alcohol has seven Calories per gram while carbs have only four. Studies on alcoholic beverages and weight gain have shown mixed results, depending on the type of alcohol consumed.

Portion size also affects how much we eat. In a recent study, people who were given large portions of popcorn ate more popcorn than people who were given smaller portions. That's not surprising. But what may surprise you is that the researchers intentionally used stale popcorn in this experiment. So even if you're not enjoying the popcorn, a big bag may make you eat more!

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account