I lost body fat but gain weight?

I've been going to the gym for 3 weeks now. I workout 5 times a week. I eat a healthy and balance diet and I've never cheated or eaten something I don't supposed to.

The thing is that today I went to the gym to weigh me and see my progress. So far I've lost 4.7% of body fat, but I gain a pound. And my workout buddy lost 3% of body fat but lost 7 ponds. What? How is that possible when both of us are following the same meal plan and we workout the same amount of times. I don't get why he lost weight and I didn't 😩 do I need to change my diet? Or workout more? Please help me
I lost body fat but gain weight?
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