The theory of weight loss that is favoured by the NHS is the idea that eating less calories and burning more calories through exercise should result in weight loss.

Some organisations even suggest that lowering calories by a set value will result in a set amount of weight loss.

It’s a nice idea but very much flawed.

The theory of calorie in, calories out

The British Dietetic Association states that: “One pound of fat contains 3,500 calories, so to lose 1lb a week you need a deficit of 500 calories a day.” [199]

So, let’s say your weight has been stable lately. Now, if you eat 300 calories fewer and burn off 200 calories through exercise each day, the theory states that you’ll have achieved a 500 calorie deficit per day -which will add up to a 3,500 calorie deficit over the week.

Hey presto, you should lose a pound of body weight each week this way.

Sadly, the reality is that it doesn’t work like this.

Would you like to be weightless?

Before we go into an explanation, let’s first take the theory to its logical conclusion and see how the theory falls apart.

Let’s say we weigh 90kg (200 lbs) and we do what we mentioned above; we have 300 kcal less per day and burn off 200 kcal through exercise to burn off a pound of body fat every week.

  • If we kept this up for a year, we’d lose 50 lbs of weight. Sounds great.
  • If we did this for two years, we’d lose 100 lbs and halve our body weight.
  • If we kept going for four years, we’d weigh zero lbs – we’d be weightless!

Would this really happen? The answer is of course a resounding ‘no’.

So let’s look at why this doesn’t happen.

The body knows how to regulate weight

Research shows that when people simply reduce their calorie intake, some weight is lost but that’s not all that happens. The body also compensates for the reduced calorie intake.

An infamous 1956 research study known as the Minnesota Starvation Experiment tested the effects.

The men in the study were for 6 months on a semi-starvation diet of 1,570 calories a day.

The men did lose weight but other effects were also noted. Their body temperature and heart rate decreased and their resting metabolic rate was reduced by 40 per cent.

This is very significant because it shows the body was compensating for the lack of calories by dropping its metabolic rate.

This shows that there’s simply no guarantee that if you cut 500 calories a day from your diet, you’ll lose a pound of body fat a week.

Eating less calories and gaining weight

A study from 1997 showed that between the late seventies and the early nineties, the prevalence of overweight people rose from 25% to 33%. [200]

During this time, calorie intake hadn’t gone up, it had actually dropped by 70 calories per day.

Significantly, fat intake had also dropped by 11% after following guidelines introduced in 1977 to eat less fat.

So, people were eating less calories and less fat and yet were becoming more overweight. What could have been happening?

Insulin’s effect on weight gain

A 1993 study by US researchers, tested the effects of insulin use in people with type 2 diabetes over a period of 6 months.

The participants were taking around 100 units of insulin a day and whilst the insulin improved blood glucose levels it had the distinctly undesirable effect of weight gain.

At the start of the study, the participants were on a diet of 2,023 kcal. As the study went o, the participants gained weight and reduced their calorie intake.

At 3 months, they were down to 1,918 kcal a day but had put on 7 kg. At 6 months, the end of the study, they were down to 1,711 kcal a day and still continued to put on weight, ending up 8.7 kg heavier than at the start of the study.

The message of the study is clear to see. A low-calorie diet won’t prevent you gaining weight if your body is producing or receiving high levels of insulin [201]

Stop counting calories with a low-carb diet

The beauty of a low-carb, high fat diet is that it helps lower insulin levels which helps the body burn body fat. Secondly, you can follow the diet without having to count calories.

If you follow the diet well, you can eat good, healthy food with no need to starve yourself. Body weight will come down and so will blood sugar levels. In addition, you’ll need less rather than more diabetes medication, which means fewer side effects to worry about.

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