The basics of how to lose body fat

Wanting to lose body fat is a central motivation for most people when looking to improve physique and self-confidence. It is also of great national importance too with obesity levels rising continuously over the last three decades and health-related issues connected with obesity causing the NHS more problems than it should have to deal with. Obesity isn’t something you can catch even if your genes do provide you with a pre-disposition for how you consume food and take exercise; it is wholly self-inflicted, fully preventable and completely reversible.

I must say that there isn’t anything wrong with being over-weight; each to their own, 100%. You can be happy with whoever you are and how you present yourself as a person; if this is being larger rather than being leaner, that is absolutely fine. But when people complain about being over-weight or when obesity is negatively impacting an individual’s health, as well as the time and stress of a family or national population who need to care, attend and be affected by those being over-weight, this is when change should come.

Moreover, the want to lose body fat is incredibly relative to each person. Someone with a body fat percentage of 35% who wants to drop to 20% to feel satisfied has as much of a right to seek that outcome as a bodybuilder who is looking to drop from 13% body fat to 5% body fat. Both can achieve their goals, take a similar route to get there and be happy and content with the result.

However, many people do not know how to lose body fat. Below are the basics behind how we lose and put on body fat.

How do you lose body fat?

1. Calorie output > calorie input

Food provides us with calories – energy to perform physical and mental daily tasks. All foods and meals have different levels of calories based on their composition of carbohydrates, fats and proteins. The more calories a meal contains, the more energy it provides the body to perform tasks. Fats have the highest calorie count at 9 calories per gram; proteins and carbohydrates both contain 4 calories per gram; and alcohol has 7 calories per gram.

Each day, the amount of calories that you consume through food and drink builds up. Each day, the amount of calories you expend through living, moving and thinking also builds up. If you consume less calories each day than you expend, you have a calorie deficit. For example, if you eat 2,000 calories a day, but you expend 2,500 calories, you have a calorie deficit of 500 calories. This means that your body has had to raid other internal sources of energy – such as stored body fat – in order for you to be able to perform the 2,500 calories worth of daily energy expenditure.

If you continue on this pattern, the calorie deficit mounts up day-by-day. It takes a combined calorie deficit of ~3,600 calories to lose 1lb of body fat. If you have a calorie deficit of 500 calories per day, as with the above example, and continue this for 7 days in a row, you will have a total calorie deficit over that period of time of 3,500 calories. This will mean you that you would have lost a few ounces short of 1lb of body fat.

Continue with this healthy pattern for two months throwing in a day every few weeks where you consume over your calorie output level (just for a bit of light relief and to enjoy foods that are higher in calories) and you will have lost half a stone.

This calorie deficit can be completed with or without exercise. The reason why exercise is suggested for weight loss is that it allows us to expend more calories and get a greater deficit each day whilst still consuming a healthy level of food. A calorie deficit by the food-only method is a much stricter protocol with less margin for ‘error’ in choosing the right type and amount of food each day. Plus, the add-on health benefits of exercise are well documented, so taking some sort of exercise that you enjoy is heavily advised.

2. Make your body use body fat as an energy source at rest and at play

All exercise uses a mixture of energy stores from the blood, liver, muscles and stored body fat. However, each of these stores has different levels of calories available to use for exercise and daily functionality. The blood has the lowest level mainly for short sharp quick release energy – normally just a few hundred calories – followed by the liver, muscles and last but by no means least stored body fat. For a lean man weighing 70kg with 13% body fat, there is still a colossal 80,000 calories in stored body fat available for use when mobilised. For health, the body needs stored body fat, and the lowest level it is recommended to have for normal functionality is about 5% – still 30,000 calories left in storage. But it is possible to lose body fat by increasing the amount of it that is used to perform activity rather than the other sources.

Annoyingly for our fat loss needs, you actually are most efficient at using body fat for energy when you are at rest. However, the calories used to perform ‘nothing’ is quite small. The higher the intensity of activity that you undertake, the more the body will want to use a quicker source of carbohydrate to perform it – not stored body fat. The best exercise for fat loss can be found by reading my article here but I want to highlight how to put the body in a beneficial state for mobilising stored body fat as a fuel at rest and play through the food you eat.

As I said, your body wants to use the easiest energy source to fuel you. If you reduce the amount of that easy energy source before performing exercise  then your body will look to those other sources in greater quantities. To do this, you can reduce the amount of carbohydrates you eat in the minutes, hours and days before you perform exercise. As you continue to do this gradually – please note that I do not promote complete or rapid carbohydrate reduction or starvation – your glycogen energy stores in muscles and liver will deplete. This will give you less immediate energy but means that more and more your body will rely on stored body fat to perform your activity. This happens to a point, and is harder to deal with if you are already at 10% body fat with high lean muscle mass and want to lose more body fat and keep the lean muscle. However, for the majority of people looking to lose body fat and who are not too bothered about optimum athletic performance, getting the body into this position through reducing carbohydrate intake and undertaking exercise will enable you to reduce your stored body fat levels. Combine this with point one above and you have an optimal situation for the body to lose body fat efficiently.

Remember, losing body fat isn’t a short term process – 50,000 calories between 13% and 5% body fat says so – but how to do it is an easy method to understand.

How does body fat get stored?

However, this story has two sides. There isn’t much point in burning your stored body fat efficiently if you are not clued up about how your body wants to store fat. With certain combinations of the above two methods and the below three methods, you can actually be pushing to the limit and burning stored body fat before putting some back on again within the space of 48 hours. This is the reason why many people can work really hard when exercising and then not see body fat reduction. They can then become demotivated and stop. Here are three things to be aware of for how the body stores fat:

1. By consuming over your daily calorie expenditure

As per the above, 3,600 calories is also the difference between calorie input vs output that is needed to put on 1lb of fat as well as to lose it. Because of this, unless you create that massive surplus over one day, one high calorie meal will not make you put on noticeable fat. It is the accumulative approach that sees you put on fat. However, the high calorie meal will re-fill your energy stores, meaning that your next exercise session will likely use more energy stored in the blood, muscles and liver than from body fat. Thus, consuming the same calories as you burn every day is a good bet for staying at the same weight…unless you consume high sugar foods or alcohol.

2. By consuming high sugar foods or alcohol

Not all calories are equal. The physical and chemical make up of all foods varies and the balance of carbohydrates, proteins and fats varies too from food to food. High sugar foods facilitate the secretion of insulin from the pancreas which automatically looks to store the energy from the sugar source as body fat – for full information about how high sugar foods affect insulin levels read my previous article here. At least we know, if you are performing high intensity exercise around the time of high sugar intake, the sugar rush will go towards performing your exercise to a high intensity. Alcohol, on the other hand, does not. The calories in alcohol (7g per 100g) are sugar based but cannot be used immediately by the body. Instead, the alcohol is processed by the liver and turned into stored energy before it can be mobilised as an active energy source. In short, when you consume alcohol, you can’t burn it off straight away. High sugar and high alcohol in one drink or meal and you have a perfect combination for body fat storage.

3. Eat foods with a low glycemic response for no body fat storage

This is similar to number two but it doesn’t just say that ‘sugars’ per se are the foods to avoid. The Glycemic Index is defined by as “a ranking of foods on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. They have benefits for weight control because they help control appetite and delay hunger.” Low GI foods are 55 and below. High GI foods are 70 and above.

Foods with a high refined sugar content, such as sweets or ice cream, are more obviously known to be high on the GI scale. But not all sugar is equal either. Fruit has a high sugar content but a lot of fruits are low GI such as apples, strawberries, blueberries and mangos. White rice, bread and pasta can have a low added sugar content on the nutrition label, but they are high GI foods and can create a rapid insulin response. The reason for this, and the pivotal part of understanding the response of certain foods on the body, is the amount of fibre that a food contains. The more fibre a food substance has, the slower it is digested. The slower it is digested, the more gradual the response of raising blood sugar and energy on the body. The more gradual this process, the lower the possibility that the energy digested will be turned into stored body fat. Fruit has this high fibre content from the sugars it contains, much of which isn’t actually digested by the body. White rice, bread and pasta has refined ingredients – the fibre removed by processing – so although there is a low sugar content nutritionally, the high carbohydrate content is digested and processed incredibly quickly and sent into the blood, rapidly and greatly stimulating insulin secretion. With this comes the automatic want to create stored body fat. Moreover, as high GI foods are rapidly digested, they do not make you feel full for very long as the process is completed quite quickly. Thus, not only do their inherent nutritional make up want to create stored body fat, the way that it is digested mechanically by the body means you are more likely to eat sooner, more and with greater speed by consuming high GI foods which takes you further towards the other method of body fat storage – calorie over-consumption.

How do you keep body fat off?

The above three, even if you do not perform much exercise. Your muscles will become smaller and your fitness may deteriorate without exercise, but your body fat levels will remain stable. If you are happy with your body, are happy with being physically active by just walking on a daily basis, and aren’t worried about losing some muscle and fitness, you can easily ensure that you stay the way you are by just watching your nutrition alone.


It is a simple science intertwined with artistry to lose, keep off and then not put on body fat. The reason why many people cannot do it is because exercise can be tough, as can consistency and restraint against certain foods and lifestyles. It is consistency that is key. If you have this in mind and you follow the advice above, you will lose body fat. 


Screen Shot 2015-02-18 at 18.54.59Chris James, MA O.A. Dip

Director, Head of Fitness and Nutrition

Fitness Body Pro


Chris James
Top Local Trainer Author
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