John Walker wrote that the key to weight loss was one simple principle – eat less food than your body burns. He also said, however, that learning how to do that could take time.

He also said that instead of stress being a catalyst to overeating, it could be used to channel healthy eating habits by applying three attitudes:

• Fixing your eyes firmly on the goal
• Will power
• A high tolerance for pain (physical and/or emotional)

Walker thought that ultimately weight loss was an outworking of delayed gratification in pursuit of a more worthwhile and long-term goal. He suggested that there were two steps to long-term weight loss and a healthy lifestyle- firstly the fixing of the problem of not knowing when and how much to eat, followed by a second stage of managing weight permanently.

Walker furthermore asserted that diet books generally only dealt with one of these issues- either a ‘quick fix’ short term diet to lose the weight, or ‘lifestyle change’ books that jumped into management without re-education.

The diet was created to address both of these aspects of weight loss in a practical and sustainable way, and the main focus is on maintaining a calorie deficit within the body.

Walker suggested that the main reason that people become overweight is due to ‘broken feedback’- the messages of hunger and fullness not being adequately received by the brain and leading to overeating.

He also suggested that in order to overcome this, people simply needed to approach eating as they did time management- having a watch does not force people to turn up on time, but it gives them the information they need to motivate themselves to move.

Walker also said that motivation could only be found within people themselves, but that there were certain things they could do to make themselves feel more motivated. These things were namely, make the steps of success easy and the thought of failure hard to contemplate, leading to the feeling of empowerment.

Walker talked about the human body as if it were a rubber bag, receiving and getting rid of food products through burning energy and waste disposal. He described fat cells as miniature rubber bags- once inflated with fat for the first time it is stretched and is more ready to expand again should excess fat become available. When lots of the miniature rubbed bags expand, so does the overall ‘bag’ of the body- this is the process of putting on weight.

Conversely, when the bag receives less food that it needs to function, it takes energy from the fat cells to be released around the body. This causes the fat cells, and the overall body, to shrink- this is the process of losing weight.

Walker explains in the book that weight loss can be reduced to simple maths. One pound of fat contains 3500 kcal, and so when we consume 3500 more calories than we burn, we will put on one pound of weight.

This can be all at once or over time – the example Walker gives of gradual weight gain is that just 250 extra calories per day will lead to a weight gain of 25 pounds in a year.

In order to lose weight, then, people simply need to consume 3500 fewer calories than they consume to lose one pound of fat. Walker said that this piece of mathematics was the most important information for people who wanted to lose weight and that anything they did to ensure a calorie deficit to this degree was simply details.

Firstly, the diet suggests using computer based tools (such as spreadsheets) to maintain and track your weight and other measurements. The book explains to readers how to use Excel to input their data in metric or imperial measurements. Dieters should also purchase an accurate electronic scale.

Dieters should log their daily weight along with their monthly weight and ‘rung’ level, and create a graph with Excel each month to show progress.

The Hacker’s diet recommends eating a balanced diet with all main nutrient groups, in order to ensure that the body gets all the ‘building blocks’ that it needs to repair and maintain itself. It suggests that the dieter finds out their probably calorie need each day from the Hacker’s chart (an average medium build woman of 5’4” would need around 1770 calories for example) and subtract 500 calories from it – at this rate of energy consumption the person will lose one pound per week.

No food is banned – only the calories are counted, although for health reasons Walkers recommends a diet fairly low in fat and containing fresh produce. Along with this he explains that frozen ready-meals can help people on the diet as they are pre-packaged and therefore easy to keep count of the nutrition values.

Walker suggested planning meals so that calories in food can be managed and dieters can avoid being caught out with fatty and sugar-laden processed food, or overeating due to extreme hunger.

He advises to weigh food with a scales to get accurate portion sizes, even though this may feel strange – “feeling silly sure beats feeling fat,” is a quote from his book. The recommended eating schedule is whatever works for the dieter, as only the total number of daily calories matter.

Using the daily and monthly graphs, you will be able to see how many calories you are over or under compared to your goal. To maintain weight loss you simply need to adjust your intake accordingly to ensure a 500 calorie daily deficit in order to lose one pound per week.

The Hacker’s Diet recommends that people exercise not with the goal of losing weight, but in order to increase energy, mental health and life expectancy and to reduce the risk of many diseases including heart problems and cancer.

Walker said that the odds made exercise a preferable option and that even if people didn’t believe they would feel better after exercising, there was enough evidence to assume that they would feel worse after a heart attack or similar health-related event due to lack of exercise.

The Hacker’s Diet exercise program is based around the following criteria:

• As little time spent as possible
• Time spent doesn’t increase as you progress
• It’s easy to start no matter your size and shape
• Pain-free
• No specialist equipment needed and exercise anywhere including in private if preferred
• Progress at your own pace

The structure of the Hacker’s Exercise program is a ‘fitness ladder’ with 48 rungs. The first 15 rungs are introductory and the ‘lifetime ladder’ are rungs 16 to 48. The exercises are intended to be done every day and should take 10-15 minutes in total. Dieters should start at the bottom rung and spend as long as they like on each rung until they are comfortable to move to the next rung- only one rung should be completed each day.

An example of a rung (rung 16) is as follows:

• Back bends x 14
• Sit ups x 10
• Prone lift x 12
• Push up x 9
• Steps x 340

Repeat 4 times.

Walker suggested that in order to keep motivation, dieters should occasionally do the rung 5 or 10 below their current fitness level, to remind themselves of the progress they have made.

The Hacker’s Diet can be effective in helping people lose weight thanks to its calorie reduced diet.

The maths behind the Hacker’s Diet is accurate, and people who consistently maintain a 500 calorie daily deficit will see a weight loss of one pound each week, so it will certainly work for people able to do this.

In order to retain muscle mass while losing fat and avoid constipation from inadequate nutrition, dieters should eat a high protein diet with plenty of vegetables as well as being in a calorie deficit. Willpower is essential to keep a calorie deficit of this nature so some people may find it too difficult if they feel weak or sick from lack of food.

This is a good diet for strong-minded individuals who are extremely committed to losing weight.

It is a good idea to remember that calorie intake is not the only factor when it comes to health and that a balanced diet is necessary for good muscle maintenance.

The exercise plan is a great way to start increasing physical activity and does not require any specialist equipment, making it accessible for most people.