Have you ever wondered what effect your weight will have on your new kidney or how to manage your weight after transplant? In this article, we take a look at your weight, your calorie intake, and the effect these can have on your new kidney.
Why are calories important?
A sufficient energy intake is the basis for being able to maintain all your body functions (e.g. heartbeat, breathing, circulation, etc.). It regularly happens that people face excessive calorie intake, cravings or unwanted weight gain after transplantation. Your body weight plays an important role not only for the operation but also for the time after the transplant.
Why is my weight so important in kidney transplantation?
In order to include not only the pure body weight but also the height, the so-called Body Mass Index (=BMI) is calculated. Based on this, a classification into underweight, normal weight and overweight can be made. Before and after transplantation you should always try to keep your BMI within the range of normal weight. Both underweight and severe overweight (=obesity) should be avoided, because they represent a real danger for your new kidney. There are many reasons for this.
1. Overweight in transplantation
In Germany and many other countries in Europe, access to the waiting list is restricted for people with a BMI over 35. The reason for this is a significantly increased risk of complications during and after the operation. Even after transplantation, obesity remains a risk. Significant excess weight can worsen the function of your new kidney after transplantation and lead to a decrease in your kidney function (usually determined by a measurement of the laboratory value eGFR), and even failure of your new kidney - both in the short and long term.
Additionally, being overweight remains a risk factor for your cardiovascular system and metabolism. Both systems are often stressed by kidney disease and post-transplant medications anyway.
2. Underweight in transplant
In addition, being underweight is also a danger for people after transplantation. This is mainly because transplantation, and the surgery that goes with it, puts a lot of stress on your body and your health. Therefore, your body needs reserves to fall back on in such stressful situations. Some studies show that being underweight after a kidney transplant may have negative effects on survival. Underweight people are also more likely to get sick and tend to tolerate medical therapies less well.
So you see, especially after a kidney transplant, being neither overweight nor underweight is ideal.
How many calories per day should I eat?
After transplantation, you should ideally consume 25 to 35 kcal per kg of your body weight per day. A simple example: a body weight of 70 kilos corresponds to a daily energy intake of 1,750 to 2,450 kcal. For comparison, an average meal contains between 800 and 1,200 kcal of energy. A bar of chocolate contains about 400 kcal. If you weigh less than 60 kilos, you should calculate with 35 kcal per day per kilo of your body weight.
The exact value depends, however, among other things, on your BMI, your muscle mass, your physical activity level and any possible comorbidities. If you are significantly overweight, it is recommended that you work with your medical team and nutritionists specializing in kidney disease to determine an individual daily guideline and adjust it regularly. If in doubt, you can also ask about surgical options to support weight loss (e.g. bariatric surgery to alter the gastrointestinal tract to facilitate weight loss). You may also need to adjust your daily calorie intake if you are underweight. You should always discuss your exact target range with your medical and dietary teams.
What is considered overweight or underweight?
To calculate your optimal weight, your BMI is usually used. BMI is calculated – as you already know - from your body weight and your body size and helps you to better interpret your weight. To calculate your BMI, your body weight is divided by the square of your height. Don’t ask why, but it has been agreed that this is helpful. The unit of BMI is kg /m². To better interpret your BMI, appropriate categories have been established.
What else should I consider?
The BMI alone can sometimes be misleading. For example, you may have a BMI that falls in the normal range but your muscle mass could be significantly too low. On the other hand, your BMI could be elevated because of water retention. It is therefore advisable to discuss your weight in detail with your treating team and to include your hip circumference. For men, a hip circumference of over 102 cm and for women, a hip circumference of over 88 cm is usually considered to be increased and is an indication of overweight.
How can I ensure that I'm eating the appropriate amount of calories?
It is important that you continue to eat a healthy, balanced diet after your kidney transplant. This includes not only the right amount of calories, but also the quality of your food. Make sure your protein intake is high enough and discuss this in more detail with your medical team. You should also make sure that you base your total calories for the day on your current BMI. You should also discuss this value with your healthcare team and your nutritionist.
At the same time, regular weigh-ins should be part of your routine. To keep an eye on your weight in the long run, you should measure your weight again and again. As mentioned above, your waist circumference can also be helpful to distinguish between weight changes due to water retention or an actual increase in body mass. If you are unsure what the change in your weight is due to, you should contact your kidney team.
So, in summary, not only a low or high BMI, but also continuous changes in your weight or changes in your hip circumference may be important to assess your current caloric intake.
You can also document your daily calorie benchmark in the Mizu app. This way you can easily check if you are eating enough calories. Useful tools like your food diary or Mizu's food checker will help you. And you also get important information at a glance.
