What is Lean Body Mass and Why Does It Matter?
- eileencrawford
- Dec 15
- 3 min read
Updated: 6 days ago
Discover the role of lean mass in achieving a healthy body composition
When it comes to achieving a lean body composition, we often focus on the number on the scale — but what really matters is what that number represents. True progress is improving body composition through fat loss that preserves what’s most valuable: your lean body mass.
Lean body mass plays a key role in metabolism, mobility, strength, bone health and long-term wellness, making it essential for a healthy body that looks and feels strong.
Understanding what lean body mass is, how it differs from body fat and why it influences weight can help you make meaningful progress — because real results come from preserving and building the right tissue in your body, not just watching the scale move.
What is Lean Body Mass?
Maintaining or increasing lean body mass is important for overall health, as it supports metabolism, bone health and muscle function.
Lean body mass (or lean mass) refers to the non-fat, non-bone parts of your body: your muscle, organs, connective tissue and even water within cells.
Muscle mass refers to the skeletal, smooth and cardiac tissue components of lean mass. However, skeletal muscle is what typically comes to mind when we think of “muscle”, as it makes up most muscle mass in your body and is visible and controllable.
Lean body mass gives your body its framework while muscle mass is what lets you generate force to lift, walk, run and move your body in any number of ways.
Why Should You Protect Muscle as Part of Lean Body Mass?
Muscle powers movement, strength and stability. It’s especially critical as we age and face challenging phases like menopause.
Improving body composition goes beyond the number on the scale or a lean figure. The focus should be to target the bad visceral fat while retaining or enhancing your lean body mass, which includes muscle.
The goal is a body that looks better, feels better and functions at its best.
Starting at age 30, we start naturally losing muscle. Between the ages of 40 and 80, you can lose 30 to 50 percent of your muscle mass.* Aging, being less physically active, eating less high-quality protein, a less-than-ideal diet and unhealthy weight loss all contribute to break down of muscle.**
And when you lose weight along with lean body mass, you're losing muscle, risk lowering your metabolism, weakening strength, performance and ultimately making long-term weight maintenance and healthy aging harder to achieve.
A Science-Backed Way to Improve Body Composition While Losing Weight
Science shows that the type of weight you lose matters.
In our clinical research study on our popular 5 & 1 weight loss plan, participants experienced
healthy quality weight loss. They retained 98% of their lean mass while reducing visceral fat by 14%, leading to improved body composition and greater metabolic health.†
*Patel HP, Syddall HE, Jameson K, et al. Prevalence of sarcopenia in community-dwelling older people in the UK using the European Working Group on Sarcopenia in Older People (EWGSOP) definition: findings from the Hertfordshire Cohort Study (HCS). Age Ageing. 2013;42(3):378-384.
**Volpi E, Nazemi R, Fujita S. Muscle tissue changes with aging. Curr Opin Clin Nutr Metab Care. 2004;7(4):405-410.
† In a clinical study, individuals on the Optimal Weight 5 & 1 Plan experienced a 14% reduction in visceral fat and 98% of lean mass was retained at 16 weeks.