Great question. It’s certainly possible to gain a few pounds after beginning a combined cardio and strength program, but I wouldn’t expect it so soon. A gain of 3 lbs. or so of muscle tissue has been seen in studies of adults undergoing 8-10 strength exercises for the major muscle groups, 1 set of 8-12 reps, 2-3 times a week for 10-12 weeks; during the same time frame, roughly the same amount of fat loss is also often seen, so weight can actually remain stable while body composition improves, but that is not always the case.
The most likely culprit is water retention due to dietary factors (excessive salt or carbohydrate intake) or your menstrual cycle. In any case, it’s perfectly normal for daily weight to fluctuate a couple of pounds, even if you’re limiting calorie intake and exercising regularly. To minimize frustration, avoid weighing more frequently than once a week.
Some studies find appetite increases after a workout; others report a decreased appetite. Pay attention to your desire to eat vs. physical symptoms of hunger to make sure you eat only when your body needs food. When you’re exercising regularly, it’s easy to develop an “I deserve it” attitude when it comes to high-calorie treats.
Make sure you’re keeping a meal diary; it’s easy to underestimate the amount of calories consumed. Writing it down increases your awareness, keeps you accountable, and gives you an objective record to review.
Wouldn’t it be great if we could lose weight steadily, in a straight line? Unfortunately, weight loss is often more like a gentle roller coaster. Over the course of 1-3 months, you’re on the right track if your weight generally trends downward. If not, a registered dietitian can evaluate your nutritional needs and make personalized recommendations for a meal plan that optimizes weight loss while giving you the energy you need for your active lifestyle.
Keep up the great work!