Numerous studies provide new insights into the impact of weight on the health of people on dialysis and those who have received a kidney transplant. This article explains the relationship between BMI and health during dialysis.
Weight fluctuations between dialysis sessions, known as interdialytic weight gain (=IDWG), are common. These changes are primarily due to fluid retention and removal, as dialysis cannot continuously regulate fluid balance like healthy kidneys do.
While minimizing short-term weight fluctuations is crucial, long-term weight changes unrelated to fluid retention also play a vital role in health.
What are the different BMI classes?
The body mass index (=BMI) helps categorize weight into different classifications according to the World Health Organization (=WHO):
BMI calculation can help track long-term weight trends during dialysis. The Mizu app automatically calculates BMI when you log your weight.
How does BMI impact health?
Scientific research shows that obesity (BMI ≥ 30 kg/m²) increases the risk of chronic conditions such as diabetes and cardiovascular diseases.
Conversely, being underweight (BMI < 18.5 kg/m²) can lead to fatigue, a weakened immune system, and loss of bone density (=osteoporosis). Maintaining a healthy weight is crucial for overall well-being, regardless of kidney health.
The “Obesity Paradox” in Hemodialysis
Hemodialysis (=HD) cleanses the blood through a machine. Studies on BMI and people on hemodialysis reveal an interesting paradox: while obesity is generally linked to health risks in healthy individuals, research suggests that high BMI (≥ 30 kg/m²) may actually improve survival rates in people on hemodialysis.
Conversely, underweight (BMI < 18.5 kg/m²) is associated with a higher mortality risk for people on hemodialysis. This unexpected protective effect of obesity in dialysis patients is referred to as the "Obesity Paradox." Interestingly, this paradox is also observed in other chronic conditions such as hypertension, diabetes, and heart failure.
BMI and Peritoneal dialysis
The “Obesity Paradox” is less evident in peritoneal dialysis (=PD) patients. Some studies indicate a protective effect of a higher BMI in the first year of PD, but this effect may decrease over time.
Weight and outcomes after kidney transplantation
While a higher BMI may offer short-term benefits during dialysis, its impact on health after kidney transplantation differs. Obesity increases the risk of post-transplant complications such as impaired wound healing and graft loss. Patients with normal weight generally have better long-term outcomes after kidney transplantation.
Why Does the “Obesity Paradox” exist in dialysis?
The exact cause of the “Obesity Paradox” remains debated. Some researchers suggest that excess weight provides energy reserves during critical illness. Others believe that fat tissue offers protection against inflammation or fluid imbalances in people on dialysis. Another theory suggests that more obese individuals who survive dialysis are part of a more resilient and pre-selected group of people.
What does this mean for you?
While weight management is important, there is no universal target weight for dialysis. The health benefits of obesity in dialysis do not extend to other stages of chronic kidney disease (=CKD), especially kidney transplantation.
BMI calculation helps track weight trends, but always consult your medical team to determine a healthy weight range suited to your individual health profile and goals.
