An Overview of Reducing Body Fat

Athletes, active adults, and individuals who want to lose weight also often want to reduce body fat. Having optimal levels of fat can improve your health and physical appearance. If you're an athlete, it might even give you an edge over your competitors.

Studies show that the best way to achieve an ideal amount of body fat varies from one person to the next. This means that what works for someone else may not help you reduce your body fat percentage, and vice versa.

Common Questions About How to Lose Body Fat

If your goal is to reduce body fat, it's normal to have a few questions both before you start making changes and along the way. Some of the most common questions surrounding fat loss include:

• Is spot reduction a valid way to lose body fat?
• Does an exercise fat burning zone really exist?
• Which is the best way to lose fat: diet or exercise?
• Can I increase fat loss by consuming certain foods or supplements?

If you feel overwhelmed by questions like this, rest assured you are not alone. Fat reduction is difficult for many individuals, which is partly why roughly 72 percent of the United States population is overweight or obese. But losing fat begins with setting a goal.

Fat Reduction Goals

Whether you want to lose weight for improved health or enhanced athletic performance, reducing fat is the ultimate goal. Generally, active individuals or athletes wanting to lower their body fat percentage fall into one of two categories:

1. Their body fat levels make them overfat or obese.
2. They are lean but desire additional body fat reduction, such as athletes participating in weight-sensitive sports.

Before you can decide the best way to lose your body fat, it’s important to develop a clear understanding of fat loss. Specifically, it helps to know the connection between calories, the way our bodies use energy, and how both can impact our levels of body fat.

Calories, Energy, and Body Fat

Successfully managing a consistent weight requires that you achieve an energy balance. An energy balance means that the number of calories you consume equals the number of calories you expend or burn.

Calories are units of energy taken from food that our body uses both during normal functioning (to breathe, for instance) and to engage in physical activity. A simple way to easily understand how calorie intake and expenditure can affect you over time is:

• When you take in the same amount of calories as your body burns, your weight stays the same.
• When you take in more calories than you burn, you gain weight.
• When you take in fewer calories than you burn, you have weight loss.

The easiest way to produce a calorie deficit is by both increasing output (exercise) and decreasing input (calorie intake). This depends on each individual's activity level, though. An endurance athlete burning many calories through exercise might increase their calorie intake and still lose weight.

How Food Type Can Affect Fat Loss

Carbohydrates, fats, and protein—the three macronutrients—are all essential for optimal health and fitness. The body uses carbs and fats as primary and secondary energy sources. Protein is less for increasing energy and more for building and repairing muscle tissue.

Balancing these macronutrients according to energy output is vital for reducing body fat, and each one releases a different amount of energy when consumed:

• Carbohydrates: four calories per gram
• Protein: four calories per gram
• Fats: nine calories per gram

Knowing that fat contains nine calories per gram may lead you to believe that eating less fat is the best strategy to lose fat. Yet, this is far from the truth.

Dietary Fat Does Not Always Equal Body Fat

Active adults and athletes depend on calories from all of the macronutrients to reduce body fat and preserve lean muscle. Ultimately, it is the number of calories taken in versus how many are burned that determines whether we store food as fat.

Furthermore, active adults and athletes often have higher levels of body fat when not competing due in part to a more relaxed off-season diet. However, this can lead to restricting calories when training begins, even though this is not the best method for body fat reduction.

To achieve healthy body weight and healthy body fat levels, it helps to consider the following:

• Does my goal weight promote good health and eating habits?
• Does my goal weight increase my risk of injuries?
• Does my goal weight support healthy age-related body development, including normal reproductive function?
• Can my goal weight be maintained without chronic dieting or caloric restriction, both of which could lead to disordered eating behaviors?

Other Factors Impacting Fat Loss

Other factors can influence your energy balance (thus, your fat loss) beyond just the number of calories taken in or burned. These include:

• The energy density of your diet, or how your diet is split between carbs, protein, fat, fiber, and water
• The type of energy your body uses during exercise, whether carbs or fats
• The type of exercise you do, as well as its intensity and duration 
• Any non-sport physical activities you do, like walking and doing yoga
• Whether you have a sedentary lifestyle when you're not training or working out

As you can see, many of these factors have to do with physical activity or exercise. This is because the more active you are, the more energy your body expends. When this expenditure is greater than your calorie intake, fat loss occurs.

Increasing Energy Output to Reduce Body Fat

How much fat you burn for energy changes from one person to another and this amount can depend on factors such as:

• Basal metabolic rate, or the number of calories you burn simply to survive
• Exercise activity thermogenesis (EAT), which is the number of calories burned during exercise
• Non-exercise activity thermogenesis (NEAT), the number of calories burned during non-exercise physical activity
• Thermic effect of food (TEF), the number of calories burned after eating certain foods

One way to increase your energy expenditure over time is to stay physically active throughout the day. Another is to engage in a regular exercise program.

Exercise Recommendations for Body Fat Loss

Exercise is important when trying to lose fat, because as your weight gets lower, the body experiences what is called thermogenic adaption. Thermogenic adaption refers to a slowing of your metabolism, which means that you burn less calories.

Therefore, it is recommended that athletes watch for weight loss plateaus. If these plateaus occur, you may have to make changes to your energy input (calories consumed) or energy output (physical activity) to begin to lose weight again.

Participation in a resistance training program can also increase energy output by building muscle. Eating more protein helps support muscle growth. High protein diets can also decrease adaptive thermogenesis, stimulate fat burning, and make you feel more full.

Using the Right Energy System for Fat Loss

The body uses different energy systems and, therefore, different energy sources to support our workouts. Whether this energy source is our body's fat depends on the type of exercise we do.

• During short-term, intense activities lasting five to 15 seconds (weight lifting and sprints), our body uses the phosphagen energy system. The creatine phosphate and adenosine triphosphate (ATP) stored in our muscles are a quick energy source.
• For intense exercise lasting 30 seconds to two minutes (interval training or HIIT workouts), the body uses the glycolysis system. Energy in this system is supplied through carbohydrates converted into blood glucose (sugar) or muscle glycogen (the stored form of glucose).
• In long-duration, low-intensity exercise (walking, jogging, endurance running), the body relies on the aerobic system for energy. Stored form of carbohydrates (blood glucose) or fats become the fuel to power the physical activity.

While long-duration, low-intensity exercise is best at burning fat, varying the energy systems helps our cells burn fat more efficiently. Circulation increases, too, improving fatty acid availability as an energy source during physical activity. So, aim to include all types of exercise in your workout program.

Metabolism and Body Fat

Metabolism refers to the processes our body uses to sustain life. The fuel for these processes is supplied by the things we eat and drink. The more efficient our body is at converting these fuels to energy, the hotter our internal furnaces burn.

Research shows that reducing calorie intake and weight loss can impair our internal furnaces (our metabolism) and, therefore, our energy expenditure. Other studies show that weight loss can also decrease the amount of calories burned during exercise.  

Other research suggests that when a deficit in energy intake is too severe, the body goes into adaptive thermogenesis. This can explain why weight loss plateaus occur even if you're taking in limited calories.

To avoid metabolic dysfunction and adaptive thermogenesis, it is recommended that athletes and active adults lose fat slowly. Aim for small energy deficits and monitor your progress to ensure that you're reducing your body fat in a safe and healthy manner.

Hormones Can Impact Fat Loss

Hormones also play a vital role in energy intake, energy output, and overall body composition. Hormones that can affect our ability to lose fat include:

• Thyroid gland hormones, which help regulate metabolism
• Leptin, which is made in fat cells and regulates energy availability and expenditure
• Insulin and cortisol, which are released from the adrenal glands and assist metabolic function

Unfavorable changes to these types of hormones can occur in response to caloric restriction or low body fat. The body will protect itself by holding onto energy stores and stimulating our hunger so we will eat more.

Maintaining balanced hormone function is vital while cutting body fat. According to research, small adjustments to the energy we take in (the foods we eat) work best for keeping our body functioning while still reaching our desired fat levels.

Unsafe Ways to Reduce Fat

Athletes and active adults can feel pressured to achieve ideal body composition for their sport. This causes some to resort to unsafe methods of weight loss. Voluntary dehydration, caloric restriction, and disordered eating are are a few of these methods.

In an effort to minimize unsafe weight loss methods, the National Athletic Trainers Association has provided guidelines to safely reduce body fat, which include:

• Setting reasonable weight loss goals
• Setting individualized body composition goals
• Balancing weight-related goals with optimal health and performance

Ideal Body Fat Levels

The ideal body fat level is unique to each individual. So, this percentage should take into account your health, level of fitness, and body weight goals. That said, here are general ranges to shoot for based on gender and age:

If you engage in a specific sport, this may change your ideal body fat percentage. For example, research has shown that long distance runners tend to do better when they have lower levels of body fat.

A Word From Verywell

Reducing body fat is a dynamic process for athletes, active adults, or even beginner exercisers wanting to lose weight. If this is your goal, it's important to implement proper nutrition and exercise practices to ensure a safe and healthy fat loss.

Achieving the ideal physique includes learning the best balance of energy intake and output for you. Taking it slow ensures that your body continues to run efficiently enough to support your workouts—and your health—while achieving your desired results.