1. Loss of appetite: Male cats will lose their appetite due to the influence of hormones during estrus, resulting in reduced food intake and weight loss.

2. Increased activity: Male cats will become more active in estrus, frequently looking for spouses, marking and other behaviors, which will increase their energy consumption and lead to weight loss.

3. Increased stress: Male cats' hormone levels fluctuate violently during estrus, which may cause them to feel anxious and nervous. This increase in stress will also affect their appetite and weight.

4. Consume body fat: Male cats need more energy to maintain activities and reproduction during estrus, so they will consume body fat reserves and lead to weight loss.