No you don't have to be a drill sergeant.

The facts are this, the human body is geared at survival. Fat fills several duties in the survival processes.
Not too long ago (just a couple of generations) we in the Western World suffered from famine and poor quality food just like they do in Africa today. Starvation was a way of life for millions of years. Our bodies which are driven by the sole commandment to survive are designed to convert as much food as possible into energy, either energy used right now or energy for future use during the famine.
Food has changed. We have bred and changed our food faster than we ourselves have adapted to the new age of plenty where famine and starvation never strike. Wheat and Corn (the mainstays of our diet even today) have changed. The corn and wheat of 100 years ago was smaller, less chock full of good stuff. We changed all that, we have bred huge kernels which contain more energy (sugar) and fats. Not only do we incorporate those super grains in just about everything we eat, we also feed it to other food sources like chickens, pigs and cows who in turn are bigger, juicier, and fatter.
Even the tomatoes, the lettuce the celery we have on store shelves and grow in gardens are vastly different than a few generations ago. In our drive to make enough food to feed our ever growing population we have created food which is de-constructive on the individual basis and is counter evolutionary to the processes which insured our survival for millions of years. Gardeners who grow old fashioned varieties of food will tell you that they are smaller, less sweet and tend to be less colorful. Hybrid seeds produce super foods which are brighter, fatter, sweeter and in theory contain more nutrition than their ancestors - that is dependent on how rich the soil is, unfortunately most soil is stripped off all trace elements and minerals and most fertilizers do not put those back in the ground.
Our healthy diet is in reality too healthy. Many obese people are obese even though they are eating eating right. Seriously they can't figure out what is wrong and they end up trying all sorts of things which leads to a more serious problem as the body attempts to over compensate for famine (starvation diets) and leads to a series of weight gain periods.
The Atkins diet works simply because we are starving the body of carb sources which we have genetically altered to make richer. This will have side effects, mark my words on that, in a few years we will start hearing of health issues brought on by the atkins diet being used for years and years. Each diet to date has had that happen, even the low fat diet has turned around a bit a few butts as we discovered that fats are essential and needed to preserve the health of the human body.
Being fat is a good thing, in evolutionary terms. It insured that our species made it through long lean winters and through millions of years of competition with other species. Humans are naturally fat. Of all the primates humans are more prone to a lyer of blubber than other primates. But then too we have less hair - we exchanged a fur coat for a layer of blubber. And we also decided to leave our tropical paradise for colder climates that needed more insulation for us to survive.
Body builders, Calvin Klein models, are the abnormal ones. They are beyond average and are not the typical specimen of humanity that we are programmed to believe. Indeed they are so abby normal that given the natural order of things they would not survive "nominal" stress parameters - famine. Their genetic code is such to preclude them from having higher body fat percentages, they are usually the ones who can eat just about anything they want and not gain fat, or they are genetically capable of adding weight and dropping weight at the drop of a hat. This last group is most likely to discover that come fall they star gaining weight rapidly - it is a condition keyed into light and survival through what used to be the lean times.
Most body builders have to go on a super restrictive diet a month or so before competition in order to get that 6 pack and deep lines between each muscle. Normally they have a layer of fat over all of that lean muscle mass. Again what is normal is not being shown. Most body builders are on a permanment diet, a diet which is abnormal and which is questioned by doctors today as to the long term health issues that can result from that diet.
Unfortunately some sick @#$! decided to plaster the fringe types and delude us into believing that these are the norm and that all humans can attain that look of perfection. This is just like the idea of binding girls feet to keep the feet small - some sick and perverted sense of beauty which has no grounding in reality since feet are supposed to be fairly large to support us.
It is also a matter of age:
Young Jusork, being in his early 20's is more prone to be able to have less body fat than me, the guy reaching for 40. But between you and I when he reaches mid 30 he will discover that all of that mentality of being on top of his "program" and being his own personal drill sergeant will amount to a hill of beans as his mid line begins to spread and fat begins to take over and hide all of those wonderful muscles of his youth. By that time, I will be pushing 50 and will start finding that keeping weight on is becoming a problem for as my body starts slowing down and shutting down it will lose its tendency to retain fat as readily as his does. However I will start losing that fat around my arms and legs while maintaining it around the middle. When Young Jusork is pushing 45, I will be fast approaching 60 and it can fall either way, I will either swell up like a balloon, or if genetics hold true (as my family demonstrates) I will be come thinner and thinner as my body loses interest in maintaining body fat (a secondary fuel source) Jusork will be approaching that time of life when body fat is gaining on him.
By the Time Jusork reaches my age he will have figured out that the battle of the Bulge is a no win battle, that it is a natural part of age and that in reality humans are prone to blubber and that Arnold Schwarzenegger and Cher and all of those skinny "beautiful people" are either genetically wired for abnormal low body fat, or have enough money to get lipo-suction on a regular basis.
Which brings me to another interesting fact. Even though Arnold was considered "in shape" which is an understatement, he ended up having severe health heart issues requiring by-pass operation. No matter how well he ate, how much cardio he took in, how much of a drill sergeant he was he still had a heart condition. I on the other hand can take it easy, eating all of those no-no foods I want and I have a very high chance of never having so much as a missed heart beat - why? because my family line is not prone to heart conditions, indeed only one member of my family line had heart problems and that was due to other medical conditions which were set through injury, not through genetics.
The reason why so many people are on diet and straining to lose weight is because they are straining to attain a goal which is genetically impossible.
I seriously doubt that a flat stomach is in your cards, I am even willing to bet that if you went to your doctor and had a body fat percentage measurement done that you fall well within the average or healthy range.
9 years ago I was brought to the hard cold fact that a 6-pack was beyond my genetics to reach. My doctor delivered a devastating blow to my reality when she told me that no matter how hard I crunched, no matter how restrictive I was with diet I would not form clearly defined abdominal muscles. Though I have strong abdominal muscles, there is forever a layer of fat and skin which will hide them.
Even in my mid twenties, when I was on speed for years, standing in at 6'1" tall weighing in at 128# with a waist of 28 inches I still had a layer of fat around the stomach area. I was emaciated, but still had that darn layer of fat - it is in the genes not in the diet or exercise program.
Most people are prone to that, it is natural and normal. Our society does not accept fat as normal, which betrays the reality of being human.