Given the same body weight, activity level, and muscle mass we vary very little in our caloric burn. It just wouldn't make sense if we did. The greatest variance we have would be our daily jobs. Even 1 hour of weightlifting is nothing compared to 8-12 hours of activity or lack of activity. What I meant by snake oil in this case is telling people their metabolism can vary so much that tissue loss just stops. Some will do this promising some kind of metabolism "hack". You don't just get away with running on vastly less energy.
Resting metabolic rate, diet-induced thermogenesis, exercise energy expenditure, and 24 h energy expenditure are highly reproducible. Coefficient of variation is smallest for exercise energy expenditure, followed by resting metabolic rate, 24 h energy expenditure, and diet-induced thermogenesis...
pubmed.ncbi.nlm.nih.gov
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Summary: Resting metabolic rate, diet-induced thermogenesis, exercise energy expenditure, and 24 h energy expenditure are highly reproducible. Coefficient of variation is smallest for exercise energy expenditure, followed by resting metabolic rate, 24 h energy expenditure, and diet-induced thermogenesis. There is considerable variability in total daily energy expenditure, largely due to variations in nonexercise activity. Although the factors that impact upon nonexercise activity are understood, their contribution to variation in total daily energy expenditure is unclear."
What a lot of people do when dieting and hitting a "plateau" is that they don't change anything over time. When you become smaller and lighter, your energy needs go down obviously. You're moving less weight around daily. They also lose muscle mass if they are restricting calories too much without enough protein and resistance training slowing their burn down even further.