This is a billion dollar question. There are so many answers, so many products, so many fitness motivators all over the internet. The goal of my post is not to motivate you or guide you to any product. I will simply go through theory and techniques that work.
First of all, the question is slightly incorrect. Sightly better question is, “how to lose excess fat?” Even better question is, “what does it take to achieve a healthier and fitter version of your body and soul?” I will try to answer these questions in this post. The good thing is you have actually identified the problem that your body has excess fat and is not in the right shape. Acknowledging this fact and aspiring to achieve fitness is a very good start.

To properly understand the weight loss (fat loss) process, we will go through some basic biological concepts. Your body is made up of cells. The number of cells is enormous, their types and varieties huge too. It is your cell (at mitochondria) that produces ATP (energy currency) which is directly used in all energy driven processes in your body. The input required to produce ATP can come from carbohydrates, fats and even proteins. Carbohydrates are hard to store in our body. Carbohydrates are used up faster in cellular metabolism in the ATP production. Fats can be stored quite easily by our body in the fat cells. As you might have guessed, these fat cells storing large quantities of fat and their expansion are responsible for your belly bulge. This doesn’t imply that these fat cells (and fat) are your enemy. In fact, fat typically provides more than half of body’s energy needs. So, fats are required in your diet and it is undesirable to reduce them to extreme extents from your diet.

Theory of losing
Suppose you started on a strict dieting plan and gradually started losing weight. What is happening in your body in such a state? You’re basically starving your body of necessary carbohydrates, proteins, fats. Imagine this. You’re going on a long straight highway on your bike. There are petrol pumps every 10km. Now, you’re putting very little amounts of petrol (say 100ml) every petrol pump. Your bike has the potential to run at 100kmph on such a great highway. However, running at 100kmph will consume petrol at incredible rates. Hence, your bike has to move slowly (35-40kmph) so that it can reach the next petrol pump. Although this is not that accurate analogy, something similar happens in the case of strict dieting. In dieting, you restrict your calorie intake to a large extent. Fat intake in case of dieting is also very low. Your body cells are starved of energy. So, what it happens is your body starts consuming fat from fat cells. Those fat cells start shrinking. One very important thing to note here is the fact that ATP generation from fat is much slower compared to ATP generation from carbohydrates. So, your cellular metabolism (like the bike with very low petrol) has to run much slower due to the shortage of ATP generating resources. As your cellular metabolism slows, you feel tired, your concentration, intelligence, physical prowess will all be significantly lower compared to your non-dieting conditions. In short, you will be a less capable version of yourself. Another thing which is noteworthy is the fact that dieting won’t kill those fat-storing cells. Study: New fat cells are created quickly, but dieting can’t eliminate them. So, as soon as you stopped dieting, your body will resume its metabolism at the normal pace and those fat starving cells will quickly regain lost fat during dieting. This happens very fast. You might have observed it yourself, that weight gain when you visit your home during holidays and stop being in any diet control.

Dieting is a lazy, painful and unsustainable way of losing weight.

What is the sustainable way of losing weight?
I will lay out the procedure later. Let’s revisit our bike example for a moment. Imagine now that instead of putting only 100mL petrol in your bike, you’re filling your bike’s tank with sufficient amounts (1L). You can go much faster say at 100kmph compared to 40kmph as you don’t have to worry about petrol shortage. Your bike consumes petrol at a much higher rate in this scenario. The same goes for your body. Suppose, you’re preparing for Army tests. You’re running 5km (under 25 minutes) every day in the mornings. That’s really a heavy energy driven task. Your muscles require incredible amounts of ATP during (and even after) the running process. So, your cellular metabolism increases and body cells start producing ATP faster. Carbohydrates and fats are utilised at a faster rate. Eventually, you will start losing weight due to faster cellular metabolism. You will not feel tired (except for the first month if you’re a beginner), your concentration, intelligence will be as good if not better than the previous state. However, you might have noticed that in some cases even running doesn’t help in the loss of your belly fat. This is because of two reasons. First is, your calorie intake might be higher and compensating for your workouts. The second reason is some areas of the body store more fat than the other areas. Your workouts might not be as effective in targeting those fat storing areas. See, cellular metabolism will not be same throughout the body during workouts. Cells of your leg muscles will be working harder compared to cells from your belly. Also, belly has huge resources of fat cells and it constantly compensates for your workouts by producing more fat. They are notoriously difficult to reduce. Compared this to say your face. Normally, your face loses fat at a faster rate and your new face with lesser fat looks more attractive. For a lot of people, reaching this stage is sufficient. They are happy with this state as they are enjoying food, doing exercises, maintaining high cellular metabolism, high blood circulation, reducing the chances of blood pressure, heart attacks, etc. However, to reduce belly fat and achieve the best possible version of your body, it will require extra dedication and some heavy workouts (especially in the beginning). How to achieve such a fit, fine, more attractive body?

Discipline & consistency (most important), a good pair of running shoes, a rucksack (for weight training)

The process I will describe will work best only when you’re highly disciplined and consistent in your workouts. The time of the workouts should be fixed, it should be on the daily basis. It doesn’t matter if it’s raining outside, or you have the cold or slight fever. As long as you can walk, you will be fine.

Diet guidelines
I have already slated dieting as a means to reduce weight in this post. However, it doesn’t mean you can eat whatever you like. The first rule of proper diet is no junk food from Mc Donalds, Dominos, KFC, etc. No heavily buttered chicken, paneer dishes. Basically, not eating outside. Typical home cooked, Indian meal is fine. You don’t need to completely eliminate oil or butter from your diet. But avoid eating too much of the deep fried vegetables, trans fats, and too much butter. It’s no brainer that butter is pure fat and it will increase the fat content of your body. My recommendation is dal, rice, vegetables, fruits, sprouts, milk (with very little to no sugar). For breakfast, traditional home cooked Indian breakfasts such as poha, paratha, idli, dosa, sambhar, etc are fine. This much is more than enough. No need to take supplements, no need to control and count calories.
From my personal experience, I don’t recommend eating non-vegetarian diet on a regular basis. Once in fourteen days is fine if you’re compensating it with enough hard work. The reason is non-veg diet slows down digestion. You also tend to overeat. So one-two days of workout might be lost, or done not as efficiently as required due to a single non-veg meal. Eggs and fishes (in little quantities) are good for your diet (optional, take only if you’re used to eating eggs, fishes).

Phase I
There are only two basic rules for this phase to achieve weight loss and a fit body.
Rule 1: Eat a slightly calorie deficient diet.
Rule 2: Daily workouts.

Rule 1

See, you have excess fat in your body. So, you may workout really hard, then eat really hard. Fat will not burn at the rate as you expected. So, eat a slightly calorie deficient diet. For this, all you have to do is don’t eat full belly. From your normal diet, just reduce a roti or two, or reduce a cup of rice, slightly reduce vegetable intake. You don’t need to miss any meal. Eat your three meals properly and also try to include sprouts and milk in your diet. You can eat fruits in between. Avoid fruit juices as they are high on sugar and calorie. You can barely eat three oranges but you can quickly drink orange juice made from 6 oranges in a sip. Follow the diet guidelines I mentioned before.

Rule 2
Daily workouts are the absolute necessity. Not only daily workouts but I would highly recommend trying the workouts I will be suggesting here. I would like to repeat again, you shouldn’t miss even a single day of workout no matter what.
Duration and timing of the workouts: I would strongly suggest at least 90 minutes of total workouts split into two sessions: morning (60 minutes) and evening (30 minutes). This is a bare minimum. If you can afford more time, it would be even better. Morning exercises are the most efficient. I have years of experience of doing both morning and evening exercises. I normally push myself more in the mornings, the time difference between my last meal and workout is quite large and the morning vibe is unbeatable. Mornings are the best part of the day and if you can make a habit of waking up before sunrise and doing the 60-minute workouts, you have already half won the battle.

Break down for each workout: Warm-ups (10 minutes), the workouts (45 minutes), cool down & stretching (5-10 minutes). These are the minimum time frame for your morning workouts.

Types of workouts
Long runs: For beginners, it’s very tough to run 5km. But that should be a bare minimum on days when you’re doing long runs. Run slowly, take your time in the beginning. Perfect your technique. After 5-6 runs, you will start noticing the difference. If you’re regular with your long runs, you’ll yourself aim for better timings and longer distances. One thing however to note is that you shouldn’t completely rely on long runs.

One of the fastest fat burning workouts. Try these at least once a week. Start with trying 80m sprints (running at 80% of your speed) 5 times. Follow each sprint with jumping, aerobics exercises. You’ll be out of breath. But push harder and harder. This is a high-intensity workout.

Weight training: Recommended at least twice a week (preferably 3 times). Fill a rucksack with weights (books). Start with 8-9 kgs (and later you can push to 15-16 kgs). Put them on, try climbing stairs and coming down slowly, steadily. You should be careful with these stair workouts. This exercise ensures full body workout. Meaning, your cells from neck, hands, chest, belly to legs will be pushed for higher ATP production. This workout is also a part of training for trekking expeditions. Doing this regularly will make you ever ready for trekking expeditions. This is one of the fun, yet difficult workout. This is what this workout looks like in the advanced stages: Stairs with a rucksack

Normal days: On normal days, you can do a mix of running, sprinting, aerobics, basic exercises. Just make sure to include a short burst of high-intensity workouts every day.

Include 5-6 minutes of abs workouts (either morning or evening) every day.

Evening workouts: Just have fun for 30-40 minutes in the evenings. Do whatever calorie burning workout or task you prefer. You can try dancing, swimming, cycling, aerobics, yoga, etc. Make sure you’re active and burning calories. Don’t be too easy on yourself. Push harder in the evenings too if you can.

Phase II
This phase begins when you’re satisfied that you have made the progress you wanted to make with your body. You can stop sacrificing the chapatis, rice that you were eating slightly lesser than the normal. This doesn’t mean you can start eating whatever you want. Junk food, buttered meal, the non-veg diet should be taken occasionally and compensated by doing extra hard workouts. Your workouts should be regular here too but you can relax a bit and reduce intensity on some days. In this phase, all you have to do is burn as many calories as you take. In the previous phase, you were burning more calories than you were taking. The duration of workouts can be slightly relaxed too. However, if you cleared phase I with substantial targets, you will reach a state where you will enjoy physical activities instead of shying away from them. Being fit, healthy, doing regular workouts will become an important and integral part of your life. You will be a changed, more attractive and more confident person. It all boils down to how disciplined and regular you’re in your workouts and diet.

The biggest reason for Amir’s incredible transformation is not because he had excellent trainers and dietitians. It’s because he had the commitment, discipline and work ethic.