I have been an athlete most of my life. >10 years as a firefighter, and often the lead or one of the leaders when it comes to physical fitness on a crew of people who are all focused on physical fitness. Yet I have never really felt my stomach was as amazing as it could be (6 pack wise). I have done tons of core work, ab exercises, and worked out every day. During fire season, we start almost every day with a hike, carrying a 25lb-35lb pack and I always opt for the extra weight of a 25lb chainsaw and fuel canisters as well, yet am out in front if we are allowed to go at our own pace.
But still, the abs!
That is, until I did a bit of research and found out it wasn't lack of muscle, but rather too much fat covering that muscle. I wouldn't call myself fat by a long shot, and my arm muscles and veins are well defined. So I decided to cut my body fat by changing my diet, since my exercise/fitness practices already occupied over 15 hours/week in the off season, and sometimes over 12 hours/day during the fire season.
I discovered macros, short for "macronutrients", categorizing all food intake to three categories: Fat, Protein, and Carbohydrates. I started tallying my macros and reduced carbohydrates, increased protein, and I didn't avoid fat. I stopped eating bread, or anything with flour in it. Almost completely eliminated sugar.
I felt great! I started losing body fat, at a rate of about 2% every month. I took my weight daily, on a scale that measures body fat, and it wasn't a straight line down. My daily numbers might look something like this: 18, 18.2, 17.6, 17.3, 17.8, 17.5, 17.6, 17.4, 17.7, 17.9, 17.4, 17.6, 17.8, 17.4, 17.3, 16.9, 17.1, 17.5, 17.4, 17.2, 16.8, etc. fluctuating by 1% or so from day to day, sometimes up, sometimes down, but a general downward trend.
I also checked my body fat using calipers, which I believe is a more accurate measure of body fat than the electronic scale.
I attribute this loss to a couple factors. Mostly I believe I stopped eating so many carbohydrates, which reduced my fat production. Also, I ate more fat, which I also think reduced my fat production. I know that sounds a little weird, but eating fat actually helps reduce fat production, but because your body has the fat it needs, it doesn't feel the need to produce more.
Another big factor is metabolism. As I already have a great metabolism from years of being an athlete, I just kept doing the same things I was doing before: exercising regularly, hydrating, and getting plenty of sleep. If you can speed up your metabolism, your body does the work for you, consuming excess fat.
Eating healthy is key. I don't follow a particular popular diet, but some of the ones that have similarities to my diet: paleo, keto, gluten free. I eat a lot of animal protein and a lot of raw food. I also make my own kefir and kombucha (my kombucha is more strong vinegary and less sweet than store bought kombucha) for probiotic benefits as well as keeping milk for long periods (I only use .25-.5 cup of milk each day in my smoothie, so a gallon of milk lasts over a month, but unless I convert it to kefir, the milk goes bad.)
Takeaways for anyone wanting to reduce body fat %: reduce carbs, exercise, sleep. Don't eat processed food or sugar.
Hope this helps someone :)