Como Calcular Peso Magro

Lean body mass (peso magro) refers to the weight of your body without fat. It represents the mass of your muscles, bones, organs, blood, and other non-fat tissues. Calculating lean body mass helps in assessing body composition, fitness goals, and nutritional needs.

What is lean body mass?

Lean body mass is an important health metric that measures the weight of your body excluding fat. It includes all tissues and organs that are not fat, such as muscles, bones, skin, organs, blood, and water. Accurately calculating lean body mass helps in understanding body composition, setting fitness goals, and monitoring progress.

There are several methods to estimate lean body mass, including:

Body composition analysis using bioelectrical impedance
Dual-energy X-ray absorptiometry (DEXA) scans
Hydrostatic weighing
Skinfold calipers
Mathematical formulas based on height and weight

The most common and practical methods for everyday use are the mathematical formulas, which we'll explore in this guide.

How to calculate lean body mass

Calculating lean body mass involves using formulas that estimate the weight of non-fat tissues based on your height and weight. The most widely used formulas are:

Boer formula
James formula
Hume formula

Each formula has its own assumptions and limitations, so it's important to understand which one might be most appropriate for your needs.

Note: These formulas provide estimates and may not be 100% accurate. For precise measurements, consider using professional body composition analysis tools.

Lean body mass formula

The three main formulas for calculating lean body mass are:

1. Boer Formula

Lean Body Mass (kg) = (Height (cm) × Height (cm) × 0.0022) + 0.328 × (Weight (kg) - (Height (m) × Height (m) × 0.0022 × 14.5))

This formula is based on the assumption that the average person has 14.5% body fat. It's commonly used for athletes and fitness enthusiasts.

2. James Formula

Lean Body Mass (kg) = 1.1 × Weight (kg) - 128 × (Weight (kg) / (Height (cm) × Height (cm)))²

This formula is often used in clinical settings and is considered more accurate for people with higher body fat percentages.

3. Hume Formula

Lean Body Mass (kg) = 0.32810 × Weight (kg) + 0.33929 × Height (cm) - 29.5336

This formula is based on a large sample of healthy adults and is considered one of the most accurate for general population use.

Each formula has its strengths and weaknesses, so choosing the right one depends on your specific needs and the population you're analyzing.

Example calculation

Let's calculate lean body mass for a person who is 170 cm tall and weighs 70 kg using all three formulas.

Boer Formula

Lean Body Mass = (170 × 170 × 0.0022) + 0.328 × (70 - (1.7 × 1.7 × 0.0022 × 14.5))

= (489.4) + 0.328 × (70 - 4.48)

= 489.4 + 0.328 × 65.52

= 489.4 + 21.31

= 510.71 kg

James Formula

Lean Body Mass = 1.1 × 70 - 128 × (70 / (170 × 170))²

= 77 - 128 × (70 / 28900)²

= 77 - 128 × 0.0000082

= 77 - 0.105

= 76.90 kg

Hume Formula

Lean Body Mass = 0.32810 × 70 + 0.33929 × 170 - 29.5336

= 22.967 + 57.3113 - 29.5336

= 50.7447 kg

As you can see, the three formulas produce different results. This highlights the importance of choosing the right formula based on your specific needs and the population you're analyzing.

FAQ

Which lean body mass formula is the most accurate?

The most accurate formula depends on the population and context. The Hume formula is generally considered one of the most accurate for general population use, while the Boer formula is often preferred for athletes and fitness enthusiasts.

Can I calculate lean body mass without a formula?

While formulas provide estimates, the most accurate way to measure lean body mass is through professional body composition analysis tools like DEXA scans or bioelectrical impedance analysis.

How often should I calculate my lean body mass?

It's recommended to calculate your lean body mass regularly, especially if you're tracking fitness progress or making changes to your diet and exercise routine. A good starting point is every 1-3 months.