The human body is designed to get up in the morning and look for food. This means that we are designed to move for a good portion of each day. Gathering activities do not require running all day. Hunting requires mostly stalking, with some sprinting and carrying of the carcass. Our genes have optimized us for this behavior. Our grandparents' only exercise was daily living. Obesity affected one in ten back then. We spend way more time in the gym today, yet two out of three are overweight. What is going on?
YOU CAN'T EXERCISE YOUR WAY OUT OF A BAD DIET.
The first thing to do is clean up the diet. This is eighty percent of the equation. Eight hours of sleep per night and stress reduction are the two other important parts of the equation. Once those parameters are sufficiently taken care of, proper movement rounds out the prescription for total health.
WALKING
The most important and natural movement our bodies expect is walking. Hunter-gatherers would be expected to be walking for a good portion of the day. This is what our genes expect. The health benefits of regular walking are too numerous to mention, but among them are less cardiovascular disease, depression, and anxiety. Thirty minutes per day is sufficient to achieve many of the health benefits. More is better, but don't get carried away.
RESISTANCE TRAINING
As part of our survival, we would have had to carry food, water, and supplies. So, to mimic this aspect of our innate survival skills, lift heavy things like your own body weight for around ten minutes, two or three times per week. The results will be the addition or preservation of lean muscle mass, which is critical for a longer life. I like to say, "muscle is medicine". The magic happens between workouts, so don't over-train! A sample workout would be four sets of 3 pull-ups, six pushups, and 12 air squats. It only takes minutes to do this, so not having enough time is no excuse!
SPRINTING
In the course of daily life, we would have had to flee from danger periodically. Our muscles are expecting this. We have starch stored in the muscles for emergency fight-or-flight situations. If a predator is in the area, we will get away as fast as possible. Our bodies will use the stored starch in less than one minute. It will be replenished over the next several hours. The predator may still be in the neighborhood! This is where the magic lies. We liberate body fat this way.
MOVEMENT FOR FUN
If you like running marathons or doing triathlons for sheer joy, then go for it. Just don't buy into the notion that just because you can run for three hours every day, you are more healthy for it. Chances are that you are not. Building mass and stamina is stressful. The body needs adequate recovery to realize the benefits. America is full of over-trainers. Don't be one of them!
SUMMARY
Mostly walk, bike, or skate at easy levels. Fight gravity for a half hour each week by lifting anything. Finally, move as fast as you can (sprinting, biking, swimming, etc.) for a few minutes once a week.