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The Science Of Slimming

by Adam Gould
It’s official. The UK is a nation of dieters, with statistics showing 65 per cent of women and 44 per cent of men go on a diet every year to lose weight.
The Science Of Slimming

It’s official. The UK is a nation of dieters, with statistics showing 65 per cent of women and 44 per cent of men go on a diet every year to lose weight.

Dieting is big business here. The UK weight management market – estimated at around £2 billion annually – bombards us with slimming supplements and increasingly extreme diet plans that promise quick fixes for body perfection. But what does the science say about it?

Diets then and now

Years ago nutritionists promoted low-fat and calorie-restriction diets as the best ways of losing weight.

But nutritional and weight-loss science has moved on since then, and experts have discovered things aren’t quite that simple. Many now believe it’s not how many calories you eat but where those calories come from that can make or break a weight-loss effort.

For instance, fat used to be the dieter’s public enemy number one. But now the evidence suggests sugars and simple carbohydrates are the real main contributors to weight gain. What’s more, most experts now believe many fats are actually very good for you.

Butter good, butter bad, butter good

All this to-ing and fro-ing has produced an abundance of conflicting health advice. Take dairy products, for instance. Once upon a time full-fat milk and butter were considered good for you. Then health experts declared they were really bad. Then suddenly they are good again.

Our current understanding of carbohydrates has transformed the dieting landscape too. Right now it’s thought avoiding simple carbs – white bread, pasta and other high-sugar foods – is the best way to achieve weight loss. That’s because these foods deliver so much energy so quickly, it’s impossible for you to use all of it (unless you’re an elite athlete or bodybuilder, that is). And whatever energy you don’t use could be stored as fat.

But even this thinking is probably too simplistic, as experts now believe we all process food differently. This explains why some of us can eat endless carbs and never gain an ounce while others have to run an entire marathon to burn off a bowl of pasta.  

Did you know?   Want to test how well your body processes carbs? Grab three plain, unsalted crackers and a timer and try this:

  • Put one cracker in your mouth, start the timer and start chewing. When the cracker starts to taste sweet, record how many seconds have passed.
  • Repeat two more times.
  • Add up the three results and divide by three to get an average number of seconds.


The idea is that the longer it takes for that taste to change, the lower amount of amylase enzymes are produced in your mouth – which implies your body is less efficient at breaking down carbs.

An average of 14 seconds means you process carbs really efficiently. But if it takes 30 seconds or longer for those crackers to change flavour, you may not process carbs that well.

This, and other differences between individual's biology, is why some people seem to be able to eat what they want and stay slim.. whilst others seem to put on weight all-too-easily. As we are all unique, unfortunately here is no one-size-fits-all solution - you have to find your own best balance.

Weight-loss diets at a glance

Adding to the confusion about dieting is the sheer number of different weight-loss plans on offer. If you don’t know your Atkins from your Keto, here’s a guide to some of the most popular slimming diets out there:


Diet Basic Principles Pros Cons

AKA the ketogenic diet, this high-fat, moderate protein, very low carb plan aims to get your body into a state of ketosis (when you stop using glucose as your main energy source)

Fast weight loss

Brain fog, lack of energy, ‘keto’ breath, hard to sustain in the long term

Atkins, Paleo

Two popular low-carb diets, with Atkins allowing carbs reintroduced in phases. Paleo is also called the caveman diet as you only eat foods you can hunt, fish or gather

Fast weight loss

Restrictive, hard to sustain in the long term


Includes foods typically eaten in Mediterranean-bordering countries (think olive oil, fish, nuts, wholegrains and loads of veggies)

Effective for heart health

Not designed as a weight-loss diet though studies show it may help prevent weight gain


Based on traditional foods eaten in Norway, Denmark, Sweden, Finland and Iceland (lots of fish plus locally grown veg and limited processed and sugary foods)

Effective for weight loss, eco-friendly

Can be expensive and time consuming, potentially high in saturated fats

Intermittent fasting (5:2), Time-restricted eating (16:8)

Both types of fasting diets: 5:2 allows eating normally for five days and having severely restricted calories for two (fasting); 16:8 is when you fast every day for 16 hours and have all meals during the other eight

Research is limited but promising

Fasting requires discipline and isn’t for everyone

Calorie Counting

Restricts the calories you eat each day to a set number (your number will depend on your age, lifestyle and how much weight you want to lose)

No foods banned

Not all calories are equal (100 calories worth of biscuits vs 100 calories worth of fruit, for instance)


Based on low-calorie, high-water-content foods that you can eat plenty of while still losing weight (fruit and veg, for instance, but no high energy-density foods)

Keeps hunger at bay

Bans healthy fats alongside unhealthy ones

Weight Watchers Uses tailored eating plans based on your eating habits and lifestyle. Follow via an app or get more personal advice from experts

No restricted foods, supportive community

Membership fees to pay

Jenny Craig

Low-calorie, pre-packaged meals and snacks that come with weekly one-to-one diet coaching

Takes the guesswork out of portion control

Can be expensive

Blood Type

Foods are allowed and limited according to your blood type. All types have to avoid alcohol and cured meats

Eliminates processed foods

No evidence of link between diet and blood type

Clean eating No foods with artificial ingredients allowed, only whole, organic, natural foods

Limits processed foods with added sugars and salt

Expensive, time consuming and restrictive

Glycaemic Index

Encourages eating more foods that have a low glycaemic index (GI) and fewer with a high GI (low GI foods are digested and absorbed more slowly than high GI foods)

Encourages healthy eating

Can be difficult to follow


Eating more alkaline foods and fewer acid-forming foods may boost your health and help with weight loss

Encourages eating more fruit and veg

Lack of scientific back-up

Raw Food

Most food is eaten uncooked, which preserves its vitamins, minerals and enzymes

Rich in nutrients (and handy if you don’t have a cooker)

Restrictive and unsustainable in the long term


Whilst some of them will be a lot more palatable than others; if followed to the letter most, if not all, of these diets could definitely help you to get in better shape.

Can supplements help weight loss?

Certain nutrients can help speed your metabolism, improve digestion and even effect how your body uses energy and stores fat -  all potential wins as part of a weight-loss regime. However, supplements can also be a great way to replace any nutrients that might be in short supply on your chosen diet, an important consideration that often overlooked.

There’s many different ingredients associated with assisting weight loss dieting, read our Supplements for Slimming blog to find out how nutrients such as apple cider vinegar, turmeric, hemp seed oil and probiotics might be useful.

    However the big question you should be asking yourself when choosing a diet plan is, can you stick to it? There is, after all, no point in making yourself miserable on an extreme diet only to resort straight back to your old eating habits and see all the weight you lost come piling back on soon after.

    Just remember this golden rule: when it comes to diets, if it sounds too good to be true, then it very likely is. The bottom line is there is no 'magic' solution to losing weight and keeping it off for good. But if you can find a diet that suits you and your lifestyle that you can stick to for life and not just two joyless weeks, you’ll be well on your way to a leaner, healthier body.

    by Adam Gould
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