Are there any studies for this? I feel like my eating habits haven't changed between my 20s and 30s and I've also not noticed any increase in weight. Or at which age would that start? Ironically, the only thing I could find was this, saying "these results strongly suggest we may no longer be able to blame weight gain in middle age on a slowed metabolism", since metabolism changes seem to only occur at 60+
One thing that I'm sure is helping me is that I don't have a desk job. I'm in my late 30s and feel great most days. Being active and exercising can help a ton.