What is cholesterol and how can you reduce it

Tom Rothwell, Healthcare & Wellbeing Propositions Executive

How to lose weight well

Diet and Nutrition

26 April 2023

It’s an age-old question: what’s the secret to weight loss? Clue: the answer doesn’t lie in detox tea (or ‘teatoxing’), detox pills, or fasting, nor does it lie in compensating for what you’ve eaten by doing a hard session in the gym.

It’s easy to get swept up in the misinformation around weight loss, with what to eat, what not to eat, and the latest fad diets all over the media. However, what many of these avenues fail to do is to educate and empower us on the topic of fat loss. Instead, many of the most popular diets all have one thing in common, regardless of the method: creating a calorie deficit. But are they safe?

Tom Rothwell, Healthcare & Wellbeing Propositions Executive at AXA Health, is here to explain the basic science behind losing weight safely, as well as highlighting exactly what a calorie deficit is.

Weight loss v fat loss

‘I want to lose weight’ is the goal we often set ourselves but, more often than not, we really mean ‘I want to lose fat’.

Our weight can fluctuate throughout the day; this can be due to many things, such as:

  • hormones,
  • acute food/water intake,
  • carbohydrate intake,
  • the previous day’s food intake
  • and salt intake.

This is the reason why weight on the scales is not necessarily the best indicator of fat loss or gain. Considering around 60% of our body weight is water1, solely focusing on scale weight to look at fat loss or gain is pointless and potentially damaging in some cases if we then start to rely on and become obsessed with the numbers we see.

Better methods would be a body fat percentage test (if you have access) or invest in a tape measure if you wanted to track waist measurements for example.

Don’t forget that underwear sizes, clothes sizes, belt sizes, how your clothes feel on you and progress photos are all useful tools, too!

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The science behind fat loss

The body is a complex system with many interlinking parts and, when it comes to fat loss, it’s no different. But there is one thing that you need to have if you are to lose fat ahead of anything else, and that's a calorie deficit.

What is a calorie deficit?

A calorie deficit is when we expend more energy than we intake.

‘Calories in’ is simply the calories we intake through food and drink. ‘Calories out’ is a little more complex, and is made up of three things:

  • Basal Metabolic Rate (BMR) – Energy needed for all automatic and natural processes that occur in the body, for example, breathing.
  • Physical Activity Expenditure (PAE) – Energy expended through exercise (and even when we don’t feel as though we’re exercising, e.g. walking, commuting, gardening, etc.).
  • Thermic Effect of Food (TEF) – Energy needed for us to digest, absorb and metabolise food.

The government dietary recommendations on how many calories we should aim to consume in a day to maintain a healthy weight is 2,000 for women and 2,500 for men2. This is a rough guide and largely depends on how active you are (your physical activity expenditure).

It’s easier to create that calorie deficit through altering our food intake than it is to try and out run a ‘bad’ diet, but that’s not to say there isn’t a role for exercise in weight loss. There absolutely is and with it comes a whole host of other benefits, like:

  • heart health,
  • brain health,
  • improved mood,
  • self-esteem and body confidence.

But for fat loss, it’s easier to manipulate what we’re eating, rather than trying to out exercise excessive calorie consumption.

What should I do?

There is no ‘one size fits all’ approach when it comes to losing fat – as individuals we’re all physiologically different and what works for a friend may not work for you.

But there are two things that should be at the forefront of your mind when making food choices:

1) Is it a way of eating that you enjoy and can stick to?

Food is there to be enjoyed, not dreaded, or to feel guilty about.

2) Is it creating a calorie deficit?

Generally, we tend to exclude all the foods we enjoy when fat loss is the goal. But you can include these ‘enjoyment’ type foods into your diet if you are still creating that deficit.

Ultimately, this will help you adhere to a specific way of eating long term because you’re not denying yourself anything and therefore less likely to binge. You don’t always need to count calories for weight loss, although they are important; simply keeping an eye on your portion sizes goes a long way too.

Food diary

Often, we tend to underestimate how many calories we eat on a daily basis. This is where keeping a food diary with the number of calories can be useful in highlighting a few areas where you could make slightly better food choices.

Alongside your progress in body measurements, you can then start making adjustments to your calories.


As for how many calories you should drop in a day to create a deficit, this is very individual and depends on a number of factors, such as:

  • how much fat you want to lose,
  • your metabolism,
  • if you have a medical condition,
  • or your age.

A general rule of thumb is creating a deficit of around 600 calories a day3, but it really does depend on the person.

Some may feel their energy levels decline, while others may feel fine. Recording how you feel in a food diary, noting down your energy levels, mood, feelings of hunger or tiredness, are all useful clues to gauge whether the deficit might be too much.

If your weight or waist measurements aren’t decreasing, then you’re not in a calorie deficit - that’s why keeping a food diary is such a good idea to track what you’re eating.

Key takeaways

  • Try not to focus solely on scale weight to track progress.
  • Eating foods you enjoy will make healthy lifestyle choices easier to stick to in the long term.
  • Manipulating our food intake is the most effective way to create a calorie deficit and lose fat – exercise can help but it’s extremely difficult to out run a bad diet.
  • It can take time, so try to be patient, nourish your body, move more, and enjoy the journey.

Those popular diets that aim to create a calorie deficit, can often result in skipped meals or eating food we might not enjoy, leaving us undernourished, irritable and hungry. So, try to design a balanced diet that works around you and your lifestyle, as opposed to following something you don’t enjoy.


  1. Weight loss vs. fat loss: Differences explained – Medical News Today
  2. What should my daily intake of calories be? - NHS
  3. Calorie counting – NHS, Better Health

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