Much is said about it, but not everyone knows what is body mass index or BMI. The truth is that this measure, which relates to a person's weight and height, is key to assessing health status (1). 

It is essential during menopause because there is often a tendency to gain weight and accumulate fat in the abdomen during this stage. This increases the risk of developing some chronic diseases (2). 

So, if you learn what is body mass index, you have at hand a tool to improve your health. Read on, and we will tell you how to calculate it. 

What is body mass index and how to calculate it 

The BMI is a measure that results from combining a person's weight in kilograms with his or her height in meters. This gives a value that indicates whether the weight is appropriate for the height (3). 

Once you understand what is body mass index, the next thing to do is to calculate it. To do this, we use a mathematical formula, which is as follows (3,4): 

BMI = Weight (kg) / Height (m)2.  

The formula dictates that we divide the weight in kilograms by the square of the height in meters (or what is equivalent to the height in meters multiplied by itself) (4). 

Let's see it with an example: think of a person who weighs 73 kilograms and is 1.78 meters tall. Let's say we want to calculate his BMI. To do so, we follow these steps: 

1. We square the height in meters. In this case, 1.782. The result is 3.1684.
2. Now we divide the weight by the result of the previous step. So, we have 73/3.1684. The result is 23.04 and that is your BMI (4).

How to interpret this index? 

To finish understanding what is body mass index, we have to place the value obtained with the formula within the following categories (3,4): 

- Underweight: BMI less than 18.5. 

- Healthy weight: BMI between 18.5 and 24.9. 

- Overweight: BMI between 25 and 29.9. 

- Obesity: BMI of 30 or more. 

If we follow the example we used before, we will say that the person has a healthy weight, since his result was 23.04. 

However, each BMI category has its characteristics. For example:  

- Underweight: this situation is associated with nutritional deficiencies, muscle weakness, decreased immune function, and osteoporosis. The causes are varied; from a situation of prolonged loss of appetite to gastrointestinal diseases that affect the absorption of nutrients (5). 

- Healthy weight: this is the ideal category. People with this BMI are less likely to develop heart disease and type 2 diabetes (4). 

- Overweight: having a BMI above the healthy limit increases the risk of developing chronic diseases. Although not only of a physical nature, some mood disorders can also appear as a response to perceived body image (6). Even acute stress disorder can aggravate these emotional problems related to being overweight. 

- Obesity and what causes ovarian cysts: people living with obesity are more likely to suffer from stroke, heart attacks, type 2 diabetes, sleep apnoea, and joint problems. In addition, in women, ovarian cysts are closely associated with excess weight (7).  

Beyond these categories, it is important to keep in mind that BMI is an approximate measure. It should not be evaluated on its own, but in combination with others; for example, with body fat distribution or body composition percentage (4,7). 

How to use the body mass index in menopause? 

In menopause, the use of body mass index is useful for monitoring health. The hormonal fluctuations of the stage and changes in metabolism influence body weight. If you know how to calculate BMI, you can track your progress over the years (2,8). 

In general, women gain about 1.5 kg per year in perimenopause. With the BMI, you could detect a weight gain out of the expected which warns you to take preventive measures (9). 

Now that you understand what is body mass index, do not let it contribute to a harmful cycle of menopause and anxiety. Take measurements every so often and don't despair over the results.  

Consult with health professionals for a complete and detailed evaluation of your weight. 

Referencias Bibliográficas 

1. My Way Diabetes. Do I Need to Lose Weight? [Internet]. UK: NHS Greater Manchester; 2024 [cited 2024 Jun 5]. Available from: https://diabetesmyway.nhs.uk/resources/internal/do-i-need-to-lose-weight/

2. Greendale GA, Sternfeld B, Huang M, Han W, Karvonen-Gutierrez C, Ruppert K, et al. Changes in body composition and weight during the menopause transition. JCI Insight [Internet]. 2019 [cited 2024 Jun 5];4(5). Available from: http://dx.doi.org/10.1172/jci.insight.124865

3. National Health System. Calculate your body mass index (BMI) for adults [Internet]. UK: NHS; 2023 [cited 2024 Jun 5]. Available from: https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/calculate-bmi-for-adults

4. Centers for Disease Control and Prevention. About Adult BMI [Internet]. CDC; 2022 [cited 2024 Jun 5]. Available from: https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html

5. Serón Arbeloa C, Labarta Monzón L, Puzo Foncillas J, Mayor Bonet T, Lafita López A, Bueno Vidales N, Montoro M. Malnutrition screening and assessment. Nutrients [Internet]. 2022 [cited 2024 Jun 5];14(12):2392. Available from: https://www.mdpi.com/2072-6643/14/12/2392

6. World Health Organization. Obesity and overweight [Internet]. EE. UU.: WHO; 2024 [cited 2024 Jun 5]. Available from: https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

7. National Health System. Obesity. Overview [Internet]. UK: NHS; 2023 [cited 2024 Jun 5]. Available from: https://www.nhs.uk/conditions/obesity/

8. Fenton A. Weight, shape, and body composition changes at menopause. J Midlife Health [Internet]. 2021 [cited 2024 Jun 6];12(3):187. Available from: https://journals.lww.com/jomh/fulltext/2021/12030/weight,_shape,_and_body_composition_changes_at.2.aspx

9. British Menopause Society. Menopause: Nutrition and Weight Gain [Internet].The BMS; 2023 [cited 2024 Jun 5]. Available from: https://thebms.org.uk/wp-content/uploads/2023/06/19-BMS-TfC-Menopause-Nutrition-and-Weight-Gain-JUNE2023-A.pdf