I have a 24-year plot of my body weight, age 55-79. It shows three periods in my life where I resolved to lose weight and did, the first based on willpower alone, led to an 11% drop in 6 months. The second based on low carb ideas led to a 24% of body weight drop over 12 months in 2003.
I gained it all back, and have no conclusions to offer you other than a weak conclusion, "It helps to weigh yourself often". In an attempt to use that conclusion, I purchased a balance beam scale, but I found that my weight fluctuates a pound or two from day to day for no apparent reason, this despite weighing myself mornings only before drinking.
As to why everyone is fatter these days, I think it is because nowadays food tastes better, because the world has now been combed over successfully for delicious food.
I know I can get my weight down again, but I don't try because the concentration it demands is unceasing, standing above other things I wish to attend to.
OOPS! I damaged a knee. Torn meniscus. Fear of losing mobility. Really scared! Last week in March 2015. Resolved to diet.
Mainly I'm avoiding eating between meals, especially after supper. Also avoiding carbohydrates, but not fanatic about it. I had been hoping to drop about 50 lb over 50 weeks celebrating defeating my best recorded weight of 192 in 2004. I wanted to stabilize down there somewhere. But then I plateaued around 212.
Vertical axis from 193 lb to 245 lb. Horizontal axis goes from late 1992 to Oct 3, 2017. It's been plateaued about two years. I haven't come up with the resolve to break out of that.