Exercise simply doesn't cause weight loss. Even 90 minutes of hot Bikram yoga only burns about 700 calories, and the body is going to increase appetite (or decrease metabolic rate) to compensate.

There's a ton of science about it:

"Church's team randomly assigned into four groups 464 overweight women who didn't regularly exercise. Women in three of the groups were asked to work out with a personal trainer for 72 min., 136 min., and 194 min. per week,respectively, for six months. Women in the fourth cluster, the control group, were told to maintain their usual physical-activity routines. All the women were asked not to change their dietary habits [...] On average, the women in all the groups, even the control group, lost weight, but the women who exercised — sweating it out with a trainer several days a week for six months — did not lose significantly more weight than the control subjects did"

Time magazine 2009 https://www.sscnet.ucla.edu/polisci/faculty/chwe/austen/cloud2009.pdf