When it comes to assessing your health, the number on the scale—or even your BMI—only tells part of the story. Body composition (the amount of body fat vs. muscle you have) offers a far more accurate picture of your overall health and disease risk. 

Research shows that excess fat, particularly in the abdomen, can increase the likelihood of breast cancer. A meta-analysis in Frontiers in Nutrition of nearly 8 million women found that central obesity—measured by waist circumference or waist-to-hip ratio—was associated with a higher risk of breast cancer in both pre- and postmenopausal women.

Below, we’ll explore the latest research linking body composition to breast cancer risk and practical strategies for optimizing your body composition to support long-term health and cancer prevention.

The Link Between Body Fat and Breast Cancer

Excess body fat is a known risk factor for breast cancer, especially for postmenopausal women. In fact, a meta-analysis in the British Journal of Cancer found that every 5% increase in body fat was linked to about a 15% higher risk of postmenopausal breast cancer. Researchers have identified three main contributing factors.

Inflammation

Fat tissue, particularly around the midsection (referred to as visceral fat), produces chemicals called cytokines that can cause low-level, chronic inflammation. This persistent inflammation can damage healthy cells, creating an environment that promotes the growth and survival of cancer cells, according to a review in the International Journal of Molecular Sciences.

Insulin Resistance

Being overweight or obese can also lead to insulin resistance. When the body becomes resistant to insulin, it compensates by producing more. High insulin levels can stimulate the growth of breast cancer cells and inhibit their natural death, promoting tumor development, according to research in the Journal of Clinical Oncology.

Hormonal Imbalance

Fat tissue can produce estrogen, a hormone that, when elevated, is linked to an increased risk of hormone-receptor-positive breast cancers, according to an article in Scientific Reports. This is particularly true for postmenopausal people, where fat tissue becomes the primary source of estrogen.

Muscle Mass and Breast Cancer Risk

While much attention is given to excess body fat, maintaining healthy muscle mass is equally important in reducing breast cancer risk and improving outcomes for those diagnosed. A study in Discover Oncology found that women with non-metastatic breast cancer and low muscle mass, a condition known as sarcopenia, had a significantly lower survival rate compared to those with normal muscle mass.

Additionally, low muscle mass is linked to higher levels of inflammation, which, in individuals with cancer, can speed up muscle loss and negatively impact health outcomes. On the other hand, having more muscle can help counteract inflammation caused by factors like excess body fat. 

Incorporating regular strength training exercises, such as weightlifting or resistance band workouts, can help build and maintain muscle mass. These exercises not only build physical strength but also support metabolic health and improve overall quality of life.

How Body Composition Can Guide Prevention

Monitoring your body composition is a powerful tool for assessing breast cancer risk and guiding prevention strategies. Unlike weight or BMI, which can be misleading, body composition provides a clear picture of where fat is stored and how much muscle you have, both of which influence your risk.

By establishing a baseline through a body composition scan, which you can do with an InBody body composition scale, you can track changes over time and see how lifestyle choices—like diet, exercise, and strength training—are affecting your fat and muscle levels. Regular assessments allow you to detect unhealthy trends early, adjust your exercise routine, or refine your nutrition plan to maintain a healthier balance of fat and muscle.

You can also track your waist circumference, which is measured at the navel after exhaling. For many women, a goal is less than 35 inches (88 cm).

Tracking these metrics is particularly valuable for postmenopausal people, who are at higher risk for fat-related breast cancer. Maintaining or increasing lean mass (muscle) while reducing fat mass can help lower inflammation, balance hormones, and reduce overall cancer risk.

Strategies for Healthy Body Composition

By combining smart nutrition, consistent exercise, and healthy lifestyle habits, you can optimize your body composition, support your immune system, and take meaningful steps toward reducing your breast cancer risk.

In an analysis of about 180,000 women followed for many years, those who lost weight and kept it off had a lower subsequent risk of breast cancer than women whose weight stayed stable, with larger losses generally linked to larger risk reductions, according to the Journal of the National Cancer Institute.

Eat an Anti-Inflammatory Diet

Focus on eating nutrient-rich, anti-inflammatory foods such as fruits, vegetables, whole grains, and healthy fats like olive oil, nuts, and fatty fish. These foods help reduce chronic inflammation, support hormonal balance, and provide essential nutrients for overall health. 

At the same time, limit alcohol, sugary drinks, and highly processed foods, which can contribute to fat accumulation and inflammation, both linked to higher breast cancer risk.

Strength Train Regularly

A combination of resistance training and aerobic exercise is key to optimizing body composition. Resistance training builds and preserves muscle mass, which can help regulate hormones and counteract inflammation. Aerobic exercise, such as running, brisk walking, or cycling, helps reduce excess fat and improve cardiovascular health.

Aim to do at least two full-body strength-training workouts a week, as well as at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity per week, according to the Physical Activity Guidelines for Americans.

Get Adequate Sleep and Manage Stress

Adequate sleep and effective stress management are often overlooked but crucial components of a healthy body composition. Poor sleep and chronic stress can disrupt hormone regulation, increase inflammation, and contribute to fat gain, all of which can raise cancer risk. 

Aim for seven to nine hours of quality sleep per night and incorporate stress-reduction practices like mindfulness, meditation, yoga, or light outdoor activity.