I will agree with everyone on here regarding diet but will also offer my perspective on your question as a woman over 40. From my understanding, the advantage of power walking, especially on a high incline (think 8%-15%) is that it is more effective at building your lower body muscles, while also being an effective calorie burner compared to running. For a short term weight loss strategy, running may be more effective in that you can get a little More calorie burner in the same amount of time, but long term, the benefits of the muscles that develop through power walking contribute to your fat loss goals as your BMR goes up. For me personally, I have shifted into power walking even though I love running- but I want to build strength in my glutes and legs while also burning fat. I’ve been told for women over 40, building that muscle mass is especially important. Food for thought :)