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Food Energy

In terms of weight loss the most important thing to measure is the intake of food vs. expenditure of energy. Let’s make sure we understand what all of these things mean.

The dictionary defines food as “any substance your body can translate into energy.” By this definition water isn’t a food, but let’s say that it’s “anything you can eat or drink that supports your body’s energy needs.” Your body is a complex amalgam of many systems, but to simplify we’ll only be interested in the body as a mechanical and chemical system. To use a car analogy, your body needs fuel in order to function. The best part about food energy[1] is that it can be measured, so we can know (albeit sometimes with some difficulty) what’s going into our gas tanks (stomachs).

You’re probably familiar with the unit we use to measure the amount of energy in food when consumed. It’s listed on the back of every pre-packaged food item in the form of Calories.

Cal or kCal?

Prometheus stole fire from the Gods and gave it to man.
Prometheus stole fire from the Gods and gave it to man.

The Calories in food are actually kilocalories in the scientific sense. Sometimes these calories are divided into small calories and big (or large) Calories, and it’s customary to use a capital C when referring to that unit of measure, although I’ll probably use the lower-case more often because it’s less obnoxious to read that way.

Nutritionists’ calorie, kcal, or just Calorie, is the amount of energy needed to increase 1 kilogram of water by 1° C. While it’s a metric measurement, in scientific circles the use of the SI-unit “joule” is more common. In current usage the calorie almost always means the amount of energy in food, specifically.

Input / Output

How much energy does it take to burn a pound of body fat?

There are 453.6 grams per pound. You have to create a calorie deficit of 3,500 calories to burn one pound of fat. Dietary fat has nine calories per gram.

9 calories per gram × 453.6 grams = 4,082.4 calories.

Since burning a pound of body fat only takes a deficit of 3,500 calories, we can do some more simple math: 3,500 calories divided by 453.6 grams = 7.7 calories per gram of body fat, which is less than the 9 calories that we know fat to contain per gram. So why does it take fewer calories to burn the fat than it does to intake the same amount of fat?

The reason is because stored body fat, called “adipose tissue” by scientists, isn’t pure fat like the dietary fat you consume. Adipose tissue is comprised primarily of fat, but also contains protein and a lot of water. Protein only has four calories per gram as opposed to fat’s nine, and water doesn’t have any calories, so that’s why it’s biologically easier to burn body fat than to store a pound of fat due to an excess of food intake. Of course, it’s easier to sit on your ass watching TV and eating potato chips than it is to exercise, and calorie-dense & nutritionally vacant foods comprise far too much of the average diet, making losing weight harder from a psychological and practical standpoint than gaining weight is for most people. Nature is on your side, but Human Nature is against you.

Time To Lose

If you only created a calorie deficit of 100 calories per day it would take five weeks to lose a single pound of fat. To lose 1–2 pounds per week, which is the most you’ll want to lose safely (i.e. without causing harm to your body) you’ll need to create a deficit of 500–1,000 calories every day. You can do this with a combination of calorie restriction and exercise. Just keep in mind that exercise will only do so much. The 80/20 rule applies here: 80% of your weight loss will come from your diet, and 20% should come from exercise. Walking briskly only burns about 100 calories per mile. Since you’ll have to walk almost six miles to burn off one Big Mac, altering your diet will result in greater results than exercise. That doesn’t mean that exercise is useless, just that if your only goal is weight loss, exercise is less important than diet. One advantage of exercise, though, is that it increases your metabolism.

Metabolism is the way your body breaks down food, determines its constitution, and gets the right nutrients to the cells that need them. Your body burns energy all the time, even now while you’re reading this. The more physical exertion, the more energy it takes.

I was going to take some pictures of 100 calories of foods to show volumes of various foods that all have the same number of calories, but someone already beat me to it (with a gallery of what 200 calories of various foods looks like).

Take This To The Bank

Caloric intake is like having a per diem. Every day you get a certain budget, and then it resets for the next day while you sleep. The amount of calories you require on a daily basis varies from person to person, but the USDA’s guidelines for nutritional labeling of food items bases the amounts on a 2,000 calorie diet. Your needs may be more or less than that based on your weight, gender, or age. There are even variations in the metabolism of individuals, so any talk of measuring your intake vs. calories burned will be ballpark figures.

Calorie Density

Some foods are more calorie dense than others, meaning that you can eat larger amounts of some foods without taking as big of a hit in your daily budget.

Nutrient Calories Per Gram
Lipids (fats)[2] 9 calories
Alcohol 7 calories
Protein 4 calories
Carbohydrates 4 calories

Water, insoluble fiber, cholesterol, vitamins, and minerals don’t have any calories but provide other vital nutrients. Practically all foods contain some combination of the above constituents, and food calories are calculated based on the amount of fats, proteins, and carbohydrates that they contain.

How Much Of Each Nutrient Should I Eat Daily?

The Institute of Medicine provides a recommendation table called the acceptable macronutrient distribution range (AMDR) which specifies the percentages of each macronutrients (fat, protein, carbs, etc.) people should consume daily based on their age and gender. For adults, on average, you should base your percentage of macronutrient intakes on:

Macronutrient Daily Caloric Consumption
Carbohydrates 45–65%
Protein 10–35%
Fats[3] 20–35%

As you can see, the totals of the maximum range exceed 100%, so depending on your age and gender you’ll need more or less of each nutrient. Remember, however, that your body weight is a simple balance of caloric intake versus outtake. Calories are calories whether they come from fat, protein, or a jelly donut. You can get all of your calories from eating potato chips and still lose weight. You may die of malnutrition, but you’ll lose weight.

Free Energy

Your metabolism is working all the time, burning energy just to keep your vital functions working, your body heat constant, heart beating, and lungs breathing. The amount of energy needed to keep you alive is called your basal metabolic rate. BMR varies in individuals, but a good average figure is that your BMR constitutes about 60% of your total energy consumption. You also burn energy digesting food, and of course through activity.

The average woman burns 10 calories per pound, and men burn 11 calories per pound.

Let’s assume for example a 150 pound woman (because the math works out conveniently). Her BMR would result in a caloric consumption of 1,500 calories (150 lbs x 10 calories), which is 60% of a total of 2,500, which is the amount of calories she’d have to consume daily to maintain the same weight.

But like I said above, BMR varies based on a great number of factors, including genetics, body frame, height, weight, etc. It’s widely known that the BMR of overweight people is actually much greater than that of fit people since it takes more energy to keep more mass moving, and being overweight stresses the body causing an overweight person to burn more energy than if they weren’t carrying the extra weight. If you’re overweight, this is excellent news.

Your BMR constitutes about 60% of your daily caloric needs. Another 10% goes to digesting food and carrying nutrients to your organs. Only 30% of your daily caloric intake goes to powering your muscles to move your body around through activity. So it seems that you’d be well-served by figuring out how to increase your basal metabolic rate. Of course, to know how to increase it you’ll need to know how to calculate yours first.

Some fancy scales can determine your BMR by sending a small electrical current through your body (one foot to the other) and measuring the resistance caused by water in your cells. It’s a rough estimate. There are also handheld devices that can measure your body fat percentages so you can calculate your BMR more accurately. Your doctor can prescribe far more accurate tests that require expensive equipment, or by suspending you in a tank of water like Luke Skywalker in The Empire Strikes Back.

Personally, I base my intake on an 1800–2000 calorie diet and have been losing weight more rapidly than is recommended by my doctor. I’d have to recommend that you talk to your physician or dietitian to figure out how many calories you should be consuming daily, and what percentage of macronutrients you should target.

Raising Your Metabolism

Here are a few ways to boost your metabolism:

  • Exercise – Not only does exercise help make you stronger and feel better, but you get a small metabolism bump that lasts hours after you’ve finished exercising. That’s why it’s better to work out in the morning rather than at night after work (if you have to choose).
  • Build muscle – Every pound of muscle burns about 6 calories per day through general use, while each pound of fat only requires about 2 calories a day. While you can’t turn fat into muscle (they’re completely different tissues) you can increase your muscle mass through exercise and thus raise your metabolic rate slightly. The more muscle you have, the more energy you burn.
  • Don’t starve yourself. – You burn excess fat by creating a calorie deficit, but if you create too much of a deficit your body thinks it’s starving and slows down your metabolism in order to keep you alive for as long as possible.
  • Get enough sleep. – Sleep depravation slows down your metabolism. Even though you burn fewer calories while sleeping than while awake, you’ll burn fewer calories still if you don’t get enough sleep. Most adults need 7–9 hours of sleep per night.
  • Eat smaller. – I don’t mean eat smaller portions (although you should do that too) but eat smaller meals more frequently. Your metabolism slows down when you’re done digesting food, so eating smaller amounts of food spread out throughout the day will actually keep your metabolism going stronger for longer.
  • Eat more fish. – Especially those containing omega–3 fatty acids. Salmon, sardines, and other rich in omega–3 fish oils have been known to raise your metabolic burn by as much as an additional 400 calories per day.
  • Spice it up. – Studies have shown that eating spicy foods actually raises your metabolism. Some diet pills actually contain pure capsaicin, the protein that makes food taste hot & spicy. Spices also have the added benefit of adding a tasty kick to some blander (but healthier) foods.
  • Drink green tea. – Drinking green tea before a workout is said to increase the amount of calories you burn between 15 and 20%.
  • Drink coffee – The caffeine in coffee is a stimulant and slightly raises your metabolism.
  • Eat more protein. – Proteins take more energy to burn than fats or carbohydrates, which extends the amount of time you spend metabolizing your food between meals. Plus, protein is essential for promoting muscle growth, which also burns more calories.
  • Be younger – Metabolism slows with age, so the best way to speed up your metabolism is to grown younger. Oh yeah, that’s impossible. I guess you’ll have to stick to eating right and working out, then.

OR WILL YOU?!??!?

Burning Calories Through Inactivity

Did you know that you burn calories all the time? Right now reading this is burning more calories than you’d burn if you were sleeping or just sitting still on the sofa. This is sometimes referred to as NEAT – non-exercise activity thermogenesis. This is the activity that you wouldn’t consider activity – fidgeting, shivering, pacing, talking – all of these things burn a small amount of calories.

No one is going to suggest that you replace your daily 30 minute workout with fidgeting on the sofa, but by keeping in mind that just about everything you do with your body burns calories you can make a game of it by trying to burn as many calories as you can per day.

The following figures are based on the Compendium of Physical Activity, a reference that assigns a MET value (defined as the ratio of activity to a standard resting metabolic rate) to various activities based on their intensity. Sitting still is the baseline of 1.0 METs per hour. The METs are considered an average over time, which is why gardening is higher than surfing – surfing may be higher intensity for brief intervals, but constant gardening beats out waiting for that perfect wave to come.

I’d argue that sexual activity is rated far too low in terms of physical intensity, but then I’d be bragging.

Calories burned per hour
per pound of weight.
Activity Calories
Men Women
Sleeping 9.9 9.0
Sitting Still 11 10
Standing 13.2 12
Sex (moderate intensity) 14.3 13
Sitting (Reading or Typing) 16.5 15
Showering, Toweling-Off
(while standing)
22 20
Cooking (while standing) 22 20
Washing Dishes 25.3 23
Walking (light stroll) 27.5 25
Surfing 33 30
Walking (3mph) 44 40
Gardening 56 50
Moving Furniture 66 60
Bicycling 88 80

None of these things are generally considered “exercise” (except maybe bicycling, which I included because it’s not work if it’s fun, right?) yet all of these activities burn some calories. Cooking burns more calories than sitting. Reading burns slightly more calories than watching TV (I wonder if that’s because of the page turns). Walking tends to burn more calories the faster you walk, but the interesting part about walking/jogging/running is that you burn the same calories over the same distance no matter your intensity. So running one mile burns the same number of calories as slowly walking that same mile (although running will burn them faster).

So get out there and burn some calories. Or just sit here in front of your screen and burn slightly fewer calories.

Science. It works, bitches.


  1. If you’re reading a book or article about nutrition and the author refers to the “energy” in a food in some vague new-agey bullshit sense, like “carrots contain so much positive energy,” that book is garbage and should be thrown away, composted, or burned for heat. The only true “energy” in food is measurable in Calories. Also beware anyone who claims to be a “wellness expert” as that generally translates to “totally and completely full of shit.”  ↩

  2. Butter has only 7 calories per gram instead of 9 because it contains about 25% water and other solids. European butters contain only 20% water so are slightly more caloric (but creamier and more delicious).  ↩

  3. Of the 20–35% of fats, only 0.6–1.2% should be polyunsaturated, and there is no safe recommended amount of saturated or trans-fats.  ↩

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Disclaimer: I am not a doctor. I'm just some guy who lost a lot of weight and studied up on nutrition, diet, and exercise in order to improve my personal fitness. The contents of this site in no way contains medical advice. You should visit your doctor before making any dramatic changes to your diet or activity. While I make every attempt to be as accurate as possible regarding current knowledge and scientific studies (please feel free to let me know when I'm wrong about something), and may from time to time post updates to correct inaccuracies in previous entries, the information on this site is provided "as-is" for entertainment purposes only. Don't do something stupid and then sue me. I'm just trying to help. Thanks.