I believe in eating smaller meals more often throughout the day to keep the metabolism going. Don't deprive yourself, just make better choices. At 50 years old it is definitely a lot harder to stay in shape then it was when I was in my 20's. ↗
They have been deprived nutritionally, or some illness has not been picked up, or they have not been screened for vision or hearing defects, or they have not had some kind of a chronic illness or error of metabolism picked up. ↗
Around age 40 I put on twenty pounds. I had always had a perfect metabolism. But, my metabolism betrayed me as it does most people, except a very rare few who will always be thin. ↗
My advice is to give up stevia, aspartame, sucralose, sugar alcohols like xylitol and malitol, and all of the other heavily-used and marketed sweeteners unless you want to slow down your metabolism, gain weight, and become an addict. ↗