There are a plethora of myths out there that seem factual just because of a few good examples. Some think that people who wear spectacles are more intelligent. In fact, if you want to appear smarter or more cerebral than you really are, wear glasses.
The list is endless.
Many people including singers are of the belief that being obese or overweight has no contribution to better singing, yet we always assume that a fat singer is a great singer.
This is shut down when you meet a fat not-so-great singer.
I have been obese. I have weighed as much as 90kg to 97kg for as long as 6 years. At that time, my Body Mass Index ( I am 173cm tall) was between 30.1 to 32.4. That ended 5 years ago.
According to the UK National Institute of Health (NIH):
BMI less than 18.5 is underweight.
BMI between 18.5 and 24.9 is ideal.
BMI between 25 and 29.9 is overweight.
BMI over 30 indicates obesity.
In the past 5 years, I have been in the healthy weight of 67kg to 70kg, giving me a BMI range of 22.4 to 23.4.
I have been singing actively before during and after my obese phase. I did not notice any fluctuations or improvement in my vocals other than what a person experiences when they have flu, fatigue or any illness.
My personal experience is just like many others.
However, according to choirplace.com, losing or gaining significant weight can have effect on your singing voice in terms of pitch or timbre. The article states that for men who become overweight, they will produce more female hormones which will make their sound lighter. They will not be as efficient in producing strong gutsy sounds.
For women who become overweight, they will produce more testosterone and will be singing slightly lower in pitch. The article adds that underweight singers have their pitch unaffected but they are prone to vocal injury.
Looking back at overweight opera singers which was the norm, I am inclined to think that the weight gain was seen as a good thing for the vocal resilience to injury. Nevertheless, it didn’t address the problem of breath management which is better amongst physically active persons who are singers.
pubmed.gov documented an analysis of the impact of body weight and body fat volume on selected parameters of vocal quality, phonatory range and aerodynamics in females. 29 females were used in the experiment and the results say that body weight and body fat volume does appear to influence voice quality, vocal aerodynamics and phonatory range performance.
I like my current BMI.