The average American visits a doctor three times a year.

And those visits usually entail the taking of so-called “vital signs”, including blood pressure, pulse, and weight.

But emerging evidence strongly suggests that doctor visits should include measurement of a new vital sign: body composition.

Specifically, it’s becoming clear that it’s important for you and your doctor to know your proportion of muscle mass in relation to fatty tissue.

Two years ago, a Canadian team summarized the growing evidence that muscle mass has big impacts on health — and to the outcomes of treatment and hospitalization for cancer and other chronic diseases.

Based on the evidence available then, they concluded that lack of muscle in proportion to fatty tissue causes more post-operative complications, longer hospital stays, weaker physical capacities, lower quality of life, and higher risk for premature death.

A new paper from an international team examines how nutrition can affect muscle mass, lack of which worsens outcomes for people with cancer, cardiovascular conditions, and other chronic diseases.

Before turning to that new paper, let’s look at a Canadian team’s review of evidence on the topic of muscle mass and medical outcomes.

Following our look at the new paper, we'll examine more closely the impacts of muscle mass and body composition on treatment outcomes — which are greater than previously suspected.

Review found that muscle plays an overlooked health role
Nutrition expert Carla Prado, Ph.D., R.D., of Canada’s University of Alberta (pictured at right) focuses her research on how low muscle mass affects health and therapeutic outcomes.

She led the recent review of nearly 150 studies published between 2016 and 2017 (Prado CM et al. 2018).

They examined evidence concerning the effects of body composition on surgical outcomes in general and on the outcomes for people with cardiovascular disease, kidney disease, COPD, cancer, liver disease, traumatic injuries, and for hospital patients requiring ventilation.

Overall, Dr. Prado’s team concluded that patients with low muscle mass — many of whom, but not all, are overweight or obese — experience more surgical complications, longer hospital stays, and lower survival rates.

Why would that be? In part, as Prado said, “Muscle is very important for movement and balance, for posture, strength and power, but it’s also a reservoir of amino acids. The more you lose, the greater the consequences.”

In her just-published study, Prado argues that nutrition interventions could improve cancer treatment, making a high-protein, high-nutrient diet a crucial tool in the fight against a life-threatening illness.

Nutrition offers a way forward
The new paper by Dr. Prado and her colleagues focuses on nutrients that may help prevent or improve treatment outcomes for chronic diseases — especially cancer — by building muscle.

While food guidelines are often “one size fits all,” Prado believes increasing protein and muscle-building nutrients could radically improve outcomes. In other words, optimal and targeted nutrition — which often gets little more than lip service in the medical arena — should be considered a vital therapy.

“We take nutrition for granted, but it’s truly important,” she said. “Just like we need oxygen to breathe, our muscles need protein and amino acids to grow.” (Prado CM et al. 2020)

As she and her colleagues wrote in their new paper, “Many patients with cancer experience poor nutritional status, which detrimentally impacts clinical outcomes. Poor nutritional status in cancer is primarily manifested by severe muscle mass depletion, which may occur at any stage (from curative to palliative) and often co‐exists with obesity.”

However, as they noted, while we have some evidence about the nutrients that matter to muscle mass, we still don’t have enough: “The impact of nutrition interventions to prevent/treat low muscle mass in cancer is not well understood … the type of study designs, [participant] inclusion criteria, length of intervention, and choice of nutritional strategies have not been optimal, likely underestimating the anabolic [muscle-building] potential of nutrition interventions.”

In their new paper, Dr. Prado and her colleagues review the available evidence on promising nutritional strategies for preventing loss of muscle mass, which suggest these optimal ranges of intake:

  • Calories: 25–30 per kilogram (2.2 pounds) per day
  • Protein: 1.0–1.5 grams per kilogram (2.2 pounds) per day
  • Vitamins and minerals, including 600–800 IUs of vitamin D per day
  • Fish-source omega-3 fatty acids: 2.1 grams of EPA plus 1.5 grams of DHA per day
  • Branched‐chain amino acids: leucine, beta‐hydroxy beta ‐methylbutyrate, glutamine, carnitine, and creatine

Our past reports about research into nutritional impacts on muscle mass certainly support the value of omega-3s and vitamin D to building and maintaining muscle:

We’ve also reported on research into the impacts of exercise, in What's the Best Energizing, Anti-Aging Workout? and 7-Minute Fitness HIIT.

The dangers of muscle deterioration
A serious illness is like a wildfire, Prado said, draining a body’s muscle at a rapid rate, which in turn damages hormonal, metabolic, and organ functions.

“You can lose it fast, but rebuilding it takes months,” says Prado. “Can you imagine one kilo, trying to put that on in a week or so? It’s almost impossible.”

In just three days in a hospital bed, an elderly patient can lose more than two pounds (one kilogram) of muscle. Over a 10-day hospital stay, a healthy adult can lose 5% of their total muscle mass — and that loss averages 18% among patients in intensive care units.

Muscle loss makes it harder to fight illness. A 10% loss leads to impaired immunity and increased risk of infection, 20% means weakness and slowed healing, a 30% loss leaves a patient too weak to sit, and a loss of 40% of muscle mass is often fatal.

And low muscle mass leads to generally worse outcomes — including additional complications — which cause longer hospital stays, raise healthcare costs, and strain limited hospital and medical resources. Patients also end up suffering a poorer quality of life, unable to perform basic tasks like opening a bottle of water or combing their hair.

Ten years ago, as a doctoral student at the University of Alberta, Prado wanted to compare muscle mass to cancer outcomes, but had a hard time finding thin patients with low muscle mass. That forced her to focus on obese cancer patients, which led to a groundbreaking study and paper — one that’s been cited nearly 1000 times — that linked cancer patients’ outcomes to their muscle mass.

Her research has produced major implications for the way chronic diseases are treated. For example, doses of chemotherapy drugs are often based on a patient’s body weight, placing obese patients with low muscle mass at higher risk of suffering greater toxic effects.

Weight and BMI don’t do the diagnostic trick
Body mass index — a simple calculation of weight over height — fails to detect important distinctions in body type.

A couple of decades ago, researchers began noticing an “obesity paradox” among patients with chronic diseases: patients with higher BMIs — which are typically seen as unhealthful — often fared better than low-BMI patients.

And Dr. Prado believes the solution to that mystery lies beneath the surface: it’s the proportion of muscle in the body of someone with a high, “unhealthy” BMI, she argues, that really matters.

As she says, people with the same body weight look the same on the scale in a doctor’s office, but devices that measure body composition can reveal very different amounts of muscle and fat. For example, a sedentary wrestling fan might have a normal, “healthy” BMI, while the BMI of a super-fit wrestler like Dwayne “The Rock” Johnson would look obese and unhealthy.

The results of studies published in recent years suggest the value of using metrics other than weight and BMI to provide a fuller, more accurate picture of someone’s health. These include body composition (i.e. someone’s ratio of muscle to fat), walking speed, grip strength, and the ability to do push-ups or other exercises indicative of strength.

Regardless of how muscle mass is measured, Prado thinks it needs to be a new vital sign. Doctors should be asking patients whether they have problems getting out of their car, she said. And patients facing a disease should be asking doctors how their body composition could affect treatment.

“Every other medical field has evolved into using sophisticated techniques, so why would dietitians rely on something Hippocrates could have done?” she said. “We have to evolve.”

Prado wants to take the focus off the bathroom scale and continue looking deeper. Adding muscle—or at least retaining it—could truly mean an ounce of prevention is better than a pound of cure.

But she also thinks that nutrition strategies focused on maintaining and building muscle hold the potential to transform care for cancer and other diseases.


  • Prado CM et al. Prevalence and clinical implications of sarcopenic obesity in patients with solid tumours of the respiratory and gastrointestinal tracts: a population-based study, The Lancet Oncology (2008). DOI: 10.1016/S1470-2045(08)70153-0
  • Daly LE, Prado CM, Ryan AM. A window beneath the skin: how computed tomography assessment of body composition can assist in the identification of hidden wasting conditions in oncology that profoundly impact outcomes. Proc Nutr Soc. 2018 May;77(2):135-151. doi: 10.1017/S0029665118000046. Review.
  • Gallagher D, Ruts E, Visser M, Heshka S, Baumgartner RN, Wang J, Pierson RN, Pi-Sunyer FX, Heymsfield SB. Weight stability masks sarcopenia in elderly men and women. Am J Physiol Endocrinol Metab. 2000 Aug;279(2):E366-75.
  • Prado CM, Purcell SA, Alish C, Pereira SL, Deutz NE, Heyland DK, Goodpaster BH, Tappenden KA, Heymsfield SB. Implications of low muscle mass across the continuum of care: a narrative review. Ann Med. 2018 Dec;50(8):675-693. doi: 10.1080/07853890.2018.1511918. Epub 2018 Sep 12. Review.
  • Prado CM, Purcell SA, Laviano A. Nutrition interventions to treat low muscle mass in cancer. J Cachexia Sarcopenia Muscle. 2020 Jan 8. doi: 10.1002/jcsm.12525. [Epub ahead of print] Review.
  • The Premenopausal Breast Cancer Collaborative Group. Association of Body Mass Index and Age With Subsequent Breast Cancer Risk in Premenopausal Women, JAMA Oncol. 2018;4(11):e181771. doi:10.1001/jamaoncol.2018.1771