You shouldn’t be expecting any results after 5 days. It’s likely water weight. I’d recommend staying off the scale till at least the 3rd-4th week. That’s when changes will start to begin.
For future reference, yes muscle mass makes a huge difference, giving men a natural advantage.
If you’re going to try to compare your weight loss to his, do so in percentage body mass lost.
It’s still going to be frustrating to watch pounds melt off of him so easily, but it won’t be AS bad. That’s what my boyfriend and I do anyway.
Differences in hormones, resting metabolic rate, muscle mass can all be factors in this.
Gonna sound strange, but are you close to your period? It’s normal for women to get up to 10 lbs heavier around their menstrual cycle peak.