How Does Fat Loss Work? - Friday Strength

by Aaron Friday, 09/11/2018

When we take in more energy than we need (i.e., too many calories), our bodies store the excess as fat. Then, during periods when we don’t have access to food, that fat is converted back into energy to keep us going. Sounds like a good deal, right? Fat is a portable energy source!

What’s the Problem?

Fat is energy and energy is good, so what’s the problem? The problem is that most of us don’t need as much fat as we have – since we rarely go without food – and the excess drags us down. Physically, excess body fat burdens our organs and joints, can disrupt hormone balance, and is associated with an increased risk of many serious diseases. Emotionally, being overweight can reduce our self-esteem if we perceive the excess weight – or our inability to control it – as a personal shortcoming.

As we age, it is common to lose muscle mass and gain fat. In fact, during each decade after age 30, the average American gains 10 pounds of body weight. Accounting for this net gain is the addition of 15-20 pounds of fat combined with the loss of 5-10 pounds of muscle. So the situation is actually worse than it seems, and it continues like this for the rest of our lives unless we do something about it. Clearly, excess fat is only part of the problem. We should be just as concerned about losing muscle mass. (See Why Should We Care About Muscle Mass? (part 1).)

When Is Fat Used for Energy?

Fat burning is automatic and requires no special effort on our part. Our bodies use fat to fuel all of our low-intensity activities like reading, sleeping, breathing, walking, talking, and putting away the dishes. It is only when we work harder than this (e.g., climb stairs, walk fast, lift heavy objects) that we burn sugar instead of fat. When we return to low-intensity activity, the fat-burning process resumes. (See What Are Energy Systems? for an explanation.)

Fat burning is also interrupted by insulin spikes, which occur when we eat carbohydrates and protein. Generally, we don’t burn fat when digesting meals. Once the food is digested, however, fat burning resumes to fuel our low-intensity activity.

Specific exercise techniques are not required to burn fat. If we just allow ourselves to get hungry once in awhile by spacing out our meals, we will burn fat at various times during each day as well as when we sleep.

How Do We Lose Body Fat?

Fat accumulation is caused by eating more calories than we use over a long period of time. Fat loss requires the exact opposite: that we use more calories than we consume, consistently over a long period of time. This is called a calorie deficit. The calories we don’t get from food are supplied by our fat cells, so the fat cells shrink. For example, if your body needs 2,000 calories a day, but you eat only 1,700 calories, your fat cells will supply the other 300. If this continues day after day, you will lose a pound of body fat in about 12 days.

Of course, eating less than we’re used to feels like deprivation, so we don’t tolerate it for very long before giving up. Instead of depriving ourselves, it would be better to feed our bodies as if we care about them. We need to eat healthy food, and lots of it!

A better way to lose fat is to approach it from two angles:

Strengthen the metabolism so we use more calories all day, every day, and
Control our calorie intake by eating a lot of very nutritious food with low to moderate calorie density

What is the Metabolism?

The metabolism is the sum of the body’s processes. The term is often used in place of metabolic rate, which is the number of calories we burn every day.

The metabolism has the following components:

Resting metabolic rate (RMR), which is the number of calories we would burn if we slept all day. It is the largest component of the overall metabolism and is determined in large part by one’s height, weight, and body composition. Average RMR is about 1,500 calories per day for women and 1,650 for men.
Daily activity level, such as one’s job. Do you walk all day, work with your hands all day, stand all day? Activity requires calories, and active people can burn an extra 500 calories a day or more.
The thermic effect of food, which is the number of calories required to digest the food we eat. This is typically another 10-15% on top of the RMR, depending on how much protein is in the diet.
Exercise, which includes calories used to fuel our workouts and any lingering increase in metabolism (i.e., “afterburn”) caused by those workouts.

A food and activity tracking tool like MyFitnessPal can help you estimate your caloric needs based on your age, sex, height, weight, and activity level. It will also show you the nutritional content of your food. Even if you don’t want to be tethered to software all the time, using it for a week or two can be educational. Keep in mind, however, that apps can only estimate your caloric needs. If you thought you were in a calorie deficit for four straight weeks but haven’t lost any weight, then you know the app’s estimate is wrong. Expect to make some adjustments as you go.

Add Muscle to Strengthen the Metabolism

We can actually strengthen the metabolism, reliably and in a number of ways. We can be more active, exercise more, and increase the amount of protein we eat (which increases the thermic effect of food). These are all good things. However, the best way to strengthen the metabolism is to gain muscle mass, which increases our resting metabolic rate.

Muscle mass is metabolically active tissue. In fact, muscle burns three times as many calories as fat while at rest. The more muscular we are, the more calories we will burn every day and night without even trying.

The only way to gain muscle mass – and preserve muscle as we age – is to perform resistance exercise on a regular basis. Resistance exercise means weight training (with kettlebells, barbells, and dumbbells) and bodyweight calisthenics like pushups and pullups. A whole-body, weight-training session performed three days a week is an effective way to support gains in muscle mass, and it can be maintained for a lifetime. (See What Goes Into Our Class Plans? for a description of our training plan.)

We also need to give our muscles enough protein for them to grow. Following a weight-training program approximately doubles one’s protein requirements compared to non-exercisers (see How Much Protein Do I Need?).

Exercise the Muscles

Working muscles are even more metabolically active than resting muscles. This is why exercise burns more calories than playing video games or watching TV. All types of exercise burn more calories than sitting around, but certain kinds of exercise are better for increasing the metabolism. The best types of exercise:

Support gains in muscle mass, which increases the RMR. As mentioned, the only way to increase muscle mass is to perform regular resistance exercise (using kettlebells, barbells, etc.).
Work multiple muscle groups at once. The more muscle tissue you work, the more calories you burn. “Whole body” exercises such as snatches, push presses, swings, squats, lunges, and deadlifts use the most calories because they work a large amount of muscle tissue at the same time.
“Stress” the metabolism; that is, create a large oxygen debt that must be paid back over the next day or so during the recovery period. In particular, high-intensity sets that last from 30 seconds to 2 minutes place a heavy stress on the glycolytic energy system and create a large oxygen debt. (See What Are Energy Systems? for an explanation.)

To summarize:

We want to gain muscle mass, which increases the RMR, meaning we’ll burn more calories all day long, every day.
The more muscle mass we have, the more work we can do during our exercise sessions and the larger oxygen debt (i.e., “afterburn”) we create during the recovery period.
Eating enough protein, which is required for muscle repair and growth, also increases the metabolism via the thermic effect of food.
No special activity is required to burn fat.

Now, let’s talk about what to eat. We should eat healthy food, and lots of it! But, we still need to control our calories if we want to lose excess fat.

Protein

For people who are trying to lose fat, protein has multiple functions. The most important of these is to preserve and build muscle mass. Since muscles are made out of protein, we need to eat a lot of protein to support muscle growth.

Protein requirements actually increase for people who are trying to lose fat. This is because protein has a muscle-sparing effect – it protects muscle mass from being burned as energy during a prolonged calorie deficit. If we don’t protect our muscle mass during weight loss, we will lose some of it, maybe a lot of it. To protect our muscles, we simply must eat enough protein.

As an aside, we should also limit weight loss to 0.7% of bodyweight each week to protect muscle mass. That’s about 1 pound/week for a 150-lb person, or 2 pounds/week for a 300-lb person. If we lose weight too quickly, our bodies go into a sort of “starvation” mode in which fat is actually preserved. That is obviously not what we want.

Protein is also needed to recover from workouts. Every time we exercise, we induce muscle damage that must be repaired with protein. This is a vital aspect of exercise recovery. Since we need to recover from our last workout in time for our next workout, it is important to get enough protein every day.

People who are trying to lose fat, gain muscle, or get stronger (or all three) need between 1.5 and 2.0 grams of protein per kilogram of body weight per day. For a 70kg (154-lb) person, this amounts to between 105 and 140 grams of protein per day. We should take this seriously. (See How Much Protein Do I Need? for more information.)

Carbohydrates

While protein provides the “substance” of our muscles, carbohydrates provide the energy for resistance exercise. Specifically, glycogen, which is a stored form of carbohydrate in our muscles, provides the energy. After we work out, we need to replenish this glycogen by eating carbohydrates. This is another important aspect of exercise recovery.

An average person has about 1,600 calories worth of carbohydrates stored as glycogen in the muscles. During a tough, high-volume workout, we might use about 400 calories of this energy source, which we then need to replenish by eating about 100 grams of carbohydrates (at 4 calories per gram). The sooner we do this after working out, the quicker we recover and the sooner we can work out again at our full capacity. If we avoid carbohydrate-containing foods at this time, we postpone this aspect of recovery.

However, when we eat more carbohydrates than are needed to replenish glycogen, the excess is stored in our fat cells like any other extra calories. For example, if we need 400 calories (100 grams) of carbohydrate to replenish our glycogen, but instead we eat 1,100 calories, the extra 700 calories are stored in our fat cells. Although we’ll use up this fat eventually while in a calorie deficit, it may be better to avoid fat storage if we can.

Eat Good Carbohydrates

Unprocessed, complex carbohydrates like whole, actual grains (oats, rice, and quinoa – not bread and pasta), legumes, fruits, and starchy vegetables (like corn and potatoes) give us a lot less to worry about with regard to fat storage. It is very difficult to overeat these foods without smothering them in cheese, butter, sugar, and the like. Go ahead and try it. Eat a whole baked potato with only salt, pepper, and maybe a little yogurt on it. Then eat another one, and then a third. Even if you succeed in eating all three of these potatoes, the calories still don’t add up to that much, and you probably won’t want to eat again for quite awhile. Whole, unprocessed carbohydrate-containing foods retain all of their water and fiber content, so they are bulky, take longer to eat, digest slowly, and make us feel fuller longer.

Eat More Food and Still Lose Fat

Research suggests that each person feels satisfied after eating a certain weight in food every day. It’s not the number of calories or the nutrients in the food that tell us when to stop eating, it’s the weight, as in a certain number of pounds of food. Some people eat about three pounds of food every day, while others eat about five pounds every day. Most people eat between three and five pounds. The type of food isn’t as important to feeling satisfied as the sheer weight of it – it could be pounds of peanut butter, crackers, brown rice, pizza, or vegetables. People just tend to become satisfied after eating a certain weight of food.

For those of us who want to lose fat and keep it off, this phenomenon presents a very exciting possibility – that we can potentially eat a lot more food than we do now and still lose fat. We just have to eat more of the right foods.

Focus on Calorie Density

To reduce calories while maintaining or even increasing the amount of food we eat, we need to prioritize foods that are less calorie-dense. Calorie density refers to the number of calories per pound of a given food. For example, a pound of grapes has 300 calories, and a pound of raisins has 1,360. Grapes are much less calorie-dense than raisins, and it’s easy to see why: grapes are full of water, and water has no calories. All unprocessed fruits and vegetables have very low calorie density for this reason. The water is intact, as is all of the natural fiber, which is also filling.

Processed foods with the water and fiber removed tend to be very calorie-dense. When we eat foods like chips, crackers, bread, and cookies, we tend to exceed our calorie limits without making much progress toward our daily 3-5 pounds of food. These foods also tend to be quite addictive, so we often eat more than we planned. The same is true for very fatty foods. It’s best to avoid them, or at least dilute them with lots of whole vegetables, fruits, grains, and lean proteins to keep our total calorie consumption under control.

The following is a sampling of common foods and their calorie densities.

40 – 200 calories per pound

In this category are strawberries and all vegetables, which are virtually impossible to overeat. Examples include:

Celery (40 calories/lb)
Iceberg lettuce (60)
Zucchini (70)
Tomatoes, romaine lettuce (80)
Asparagus (90)
Arugula (110)
Strawberries (150)
Carrots (160)

200 – 500 calories per pound

In this category are the remaining fruits, starchy vegetables, most whole grains, and some lean proteins. These foods are very difficult to overeat, and some of them are among the best foods we can eat to replenish glycogen and meet our protein requirements.

Apples and blueberries (250 calories/lb)
Greek yogurt (270)
Oatmeal and sweet potatoes (330)
2% cottage cheese (270)
Peas, bananas, and potatoes (400)
Sweet corn (430)
Cod (480)
Lentils (500)

500 – 800 calories per pound

This category includes mainly lean proteins and some starches. Even though eggs and avocados are high in fat, they are also high in water.

Walleye pike (540 calories/lb)
White rice (600)
Black beans (600)
Pork tenderloin, skinless turkey breast, skinless chicken breast (650)
Eggs (680)
Avocado (760)

Except for some additional healthy oils, the foods listed so far are the best foods we can eat. Not only do they have the lowest calorie density, they are also:

Filling and satisfying
Non-addictive, unlike sugary, fatty, and processed foods
Very difficult to overeat
The most vitamin and mineral-dense foods available

The foods listed below should be measured, eaten in moderation, and diluted with less calorie-dense foods. Some of them, like nuts, salmon, and olive oil, contain healthy fats. We should eat these healthy foods, but be aware that they can be very easy to overeat. Other foods in this final category are pure junk, and we can do without them altogether.

800 – 4000 calories per pound

Salmon (940 calories/lb)
Vanilla ice cream (940)
Pancake, plain (1,030)
Lean ground beef (1,040)
Multi-grain bread (1,200)
Pepperoni pizza (Pizza Hut) (1,320)
Raisins (1,360)
Chicken McNuggets (1,370)
McDonald’s french fries (1,470)
Blueberry muffins (1,700)
Prime rib (1,720)
Popcorn, air-popped (1,750)
Cheddar cheese (1,800)
Skittles (1,850)
Carrot cake (1,890)
Saltines (1,900)
French dressing (2,070)
Donuts (2,100)
Snickers or chocolate chip cookies (2,200)
Bacon or Ritz crackers (2,240)
Potato chips or corn chips (2,400)
Peanuts, almonds, or cashews (2,600)
Butter, margarine, mayonnaise (3,200)
Coconut oil, olive oil, lard (4,000)

What about Water and Other Liquids?

Unfortunately, most liquids don’t register on our daily food “scale.” If they did, it would be a simple matter to drink a few glasses of our favorite beverage and be quite satisfied with our intake for the day. Liquids are very heavy, so even soda pop, beer, and fruit juice are quite low in calorie density. However, since they don’t contribute to the 3-5 pounds, they just add empty calories. Liquid calories are best to avoid altogether.

An exception is vegetable soup, which has been shown to contribute to satiety due to its solid food content (i.e., vegetables). One could surmise that other soups are similar, and that milk, protein shakes, and the like probably register on the scale somewhat because they contain solids, most of which is protein.

The Right Way

We should focus on being fit, capable, healthy, and happy people. Any effort we make regarding improved body composition should push us in this direction. Whatever we’re currently doing to lose weight, we should ask ourselves if it’s making us healthier, stronger, and more energetic. We should also ask if it’s something we can sustain for the rest of our lives. The answer needs to be “yes” to both of these questions, or it’s not a good plan. Exercise and nutrition are really the only way.

Our metabolically active muscle mass is like an entity in itself. When we take care of it, we are healthier and happier people. Treat your muscle mass like you would treat a pet dog. Feed it well and give it as much exercise as it wants. Your muscles want to work! You just need to provide the opportunities and high-quality fuel.