lose a stone in 21 days channel 4

Lose a Stone in 21 Days with Michael Mosley

By Trudi Purdy, wlr team


Third and final episode airs 9pm Wednesday 19th August 2020, Channel 4

In this new 3-parter on Channel 4 Michael Mosley takes six people on a 21-day quick fix experiment to lose weight and improve health.

Inspired by lockdown weight gain (some 48% of people gained weight according to this Kings College/Ipsos survey) the working title for the series was Lockdown Diet. In keeping with this theme, Dr Mosley includes 'boosting immunity' as one of the outcomes he hopes to achieve.

The show covers one main theme each week:

Episode 1 - Diet

As you might expect from the lose a stone-in-3-weeks angle, the diet is low carb and a very low 800 calories.

Episode 2 - Exercise

Michael gives each participant a personalised exercise plan.

Episode 3 - Immunity

Michael coaches participants on boosting their immune systems.

In the first show, people are asked to guess their waist measurement - which gets some interesting results. Speaking about the programme to Emma Barnet on Radio 5 Live, Michael said that most people with obesity, men especially, do not know that their weight would be classed as obese. (You can check where you're at with our BMI Calculator.)

It's likely that all the participants will lose weight quickly if they stick to the diet plan, the calorie restriction alone takes care of that. Whether the diet, or the weight loss, is sustainable for more than a few weeks could veer towards the less likely.  

We'll wait until after the show to come to any conclusions about whether this is a 'good plan' ... watch this space!

Initial Thoughts

We're a bit concerned that Michael didn't really explain that when you drain your body of it's energy stores, you also lose a lot of pretty meaningless water with it. Let's see how the show unfolds ... 

Episode One Review

So, firstly, let me set the scene for you.

The sales of crisps and snacks rose by 33% in the week before lockdown, sales of alcohol almost doubled during, and two thirds of people admitted to putting on weight with 16% of people putting on 5lbs or more. Add to that the fact that we spend £19 million a year on biscuits, it’s not surprising that terms like Corona Kilo and Lockdown Belly are being bandied around.

However, our waistlines haven’t grown just because of lockdown. Public Health England have been concerned about our waistlines for much longer but, if you are overweight or obese and contract COVID-19, you are more likely to be admitted to hospital, or worse.

And so, enter stage right Dr Michael Mosley and his volunteers.

Mosley’s Fab Five

These five brave volunteers are probably representative of a large proportion of the UK at the moment. Already a little the wrong side of a healthy weight range, lockdown has added a bit more.

What else was there to do when many of us spent a lot of time in very close proximity to the kitchen fridge?

Taking a closer look at the volunteers, we have:

  • Adrian – 44 years old
    • His alcohol consumption has doubled during lockdown – gained 9-15lbs
  • Tracy – 50 years old
    • Lockdown takeaways have become the norm – gained 21lbs
  • Katie – 34 years old
    • Snacking now that she is not at work and at home with the children because of lockdown – gained 9lbs
  • Curtis – 30 years old
    • Moved home to his parents and has been comfort eating after, sadly, losing his nan to COVID-19
  • Sharika – 38 years old
    • Home alone and feeling isolated. As a result, has been drinking quite a lot and eating more – gained 11lbs

All five expressed the desire to lose weight and have healthier lifestyles, not just shed the pounds gained during lockdown.

Health Checks

The volunteers went through a series of health checks including fasted blood sugar test and blood pressure as well as taking their waist measurements, weighing them and making them walk a mile on a treadmill.

The he ‘crunched the numbers’ to give them their current health statuses. He said,

“Okay, so I have been looking at their numbers, looking at all the data we’ve collected, and I have to say, I’m shocked.”

Really? Are you really that shocked?

As a person who has been through medical training, Michael can't really be surprised that the group's cholesterol is high, or their ‘heart health’ and metabolic ages are higher than they should be. For me, the theatrics took away from the important message.

Good News, Bad News

Good news though! Once Michael had told them their weight etc., he went on to tell them that he would help them lose the pounds, get healthier and boost their immune system. Having a healthy diet is important for the immune system.

Bad news? He is putting them all on a very restrictive, low carb, 800 calorie a day diet, ensuring they go into ketosis.

Ketosis is Key?

Michael told viewers that, in order to lose weight, you need to deplete your body of its sugar stores to get it to switch to burning fat.

Does anyone else think he made it sound like ketosis is the only way to burn fat?

In my extensive experience with weight loss (my own included), that just isn’t true! And an extreme diet like the one he is asking his volunteers to do isn’t the only way to shift the pounds. Seemingly large weight losses brought about by ketosis in the first week includes a lot of water weight.

Creating a calorie deficit does lead to weight loss, but it doesn't need to be so extreme and ketosis is not necessary to burn fat.

As the first few days went on for his volunteers, they were experiencing some pretty unpleasant side effects like being hangry, feeling dizzy and thinking about food 24 hours a day. Shocker! Their calorie intake is so low and the foods they could eat very limited.

Michael pointed out that his approach is inspired by long-term studies, including one from Oxford University, and is suitable only for people in the overweight or obese category.

He went on to say that research has found that a short-term 800-1000 calorie diet, done with supervision, has the potential to reverse a range of health problems.

This statement left me wondering how many people watching this program, desperate to lose weight, would actually seek supervision before undertaking an 800 calorie a day diet or would they just ‘give it a go’? I found that more than a little worrying. .

People may just give up if they're going it alone and finding it very hard, leading to a feeling of failure and possibly more weight gain. Many of us find ourselves in this kind of yoyo dieting spiral. more weight through comfort eating. Michael himself says, later in the program, that 2 out of 5 people quit a diet after 7 days.

Going back to the part of his statement about ‘the potential to reverse a range of health issues’.

I just want to point out here, it’s not the 800 calorie a day diet that he is offering that reverses those health issues, it is weight loss and dramatically cutting sugar (not all and any carbs). You don't need to go to this extreme to get the benefits of weight loss and a healthier diet.

A recent study looked at the results of Intermittent Fasting (Michael advocates the 5:2 diet) and calorie counting and found it’s not the way you diet that counts, it’s more about finding a sustainable diet that suits you and following it through.

Interesting Findings on Our Perception of Healthy Weight

One section of the program saw Michael take to the streets with silhouettes of overweight and obese people. He asked passers-by whether they could guess their own waist size and what they thought of the body sizes of the people in the pictures.

Most people got their waist sizes wrong. One guy guessed his waist size to be 32” to find out that when he measured it, it was actually 42”.

And nearly everyone Michael asked about the silhouettes perceived the obese one to merely be overweight.

This was probably the best part of the program, in my opinion. As it highlighted that our perception of what is overweight or obese has changed. It is because, as a nation, we have got larger in stature and a heavier form is now the norm?

Next time, Michael introduces the volunteers to a personalised exercise plan. It will be interesting to see how they cope with adding in exercise on just 800 calories a day!

What wlr members said

Here are some thoughts on the show, good and bad, from wlr members:


"I did this 800 calorie diet a couple of years ago. I thought not being able to have a glass of wine was going to be the killer but what I actually craved was sausage rolls and pastry, I used to start drooling driving past the Greggs outlet store.

I lost 22lbs in 6 weeks. I did feel quite well on it, I ate 2 meals a day at 12 and 6, and was able to make quite filling meals.

I stopped at Christmas and the rebound was awful. and I quickly piled more weight on. I think if you do it for the 6-8 weeks recommended and have a plan for managing the step down to ordinary eating it is a good way to kickstart weightloss (at the time I was also worried about my blood pressure and wanted to try doing something to bring it down)." Selki


"It'll certainly be possible for them to lose a stone in three weeks on that allowance, I don't think that is in question. Whether it's a good idea is another matter.

I looked back at my first 3 weeks on here. My starting BMI was just under 30, I was on an allowance of about 1300 calories (plus exercise calories) and I lost 10lbs. So, it isn't necessary to starve yourself or eat a 'special diet' to lose effectively. More importantly I carried on to reach my goal and stay there. If I'd tried to eat 800 calories a day, I would never have made it past a couple of weeks even if my meals were made of magic pixie dust." Annie5


"I started fast 800 on Monday before I realised he had a new programme out. We have the book already my OH bought it but it had sat on the shelf.

So far all good, I have a bit of a headache today and making myself drink lots of water. I am also sticking to TRE/time restricted eating 16/8. This I find easy if I get up go for long dog walk and keep busy until 12 pm when I have 200 calorie lunch. I have just eaten 80g king prawns with two huge chopped up tomatoes followed by 80 gms Rachael’s full fat ginger yoghurt with raspberries. Loved every mouthful and nicely full. For me the biggest hurdle is not drinking wine in the evening but I have now managed three days and am feeling the benefits already.

I have lost 6 lbs in three days I know this could just be fluid but the rapid weight loss for me gives me very good motivation which is always a massive help." Abbie63


"I caught about 5 minutes of it. Lots of people saying they were hungry!

I reckon you could lose 7lb of bloat/glycogen. Which would mean only 7lb of fat/muscle lost in 3 weeks, which sounds perfectly doable on 800 cals a day.

But they are going to be SO hungry after 3 weeks of that that they will have to work REALLY hard not to sprint en masse to the nearest chippy." Gonk

Episode Two Review

This episode focussed a bit on exercise, a bit on support networks and a bit on snoring.

Michael's son Dan put three of the group through an HIIT workout to get their hearts pumping.

When you’ve exercised hard, the fitter you are, the quicker your heart rate returns to normal.

Michael did show off a little here by doing 40 push ups. He said,

“I don’t want to show off. Well, perhaps a bit. But I want to show that losing muscle isn’t inevitable and that even a 63-year-old like me can get stronger just by doing push ups regularly.”

Great motivation to do resistance training to build, and keep, our muscles. The more muscle you have, the more calories your body burns throughout the day.

Dan’s exercise routine looked hard work but fun with jumping jacks, squats etc. The group wore heart rate monitors so their recovery rates could be tested to see how healthy their hearts were.

Sharika, Curtis and Tracy took part in the exercise session with Dan. When they had finished their heart rates were:

  • Curtis – 155
  • Tracy – 156
  • Sharika – 150

Exercising with masks on may have made it a little more difficult for them.

After a minute, their heart rates had dropped by about 20 beats a minute. Not surprisingly, this showed they were unfit. But at least they know where they are now and can improve on those figures.

Michael recommended they do the exercises that Dan had shown them 3 or 4 times a week.

Flexibility is important too. Later in the episode the group took part in an online yoga session. Online classes have been very popular during lockdown coming 3rd for preferred exercise behind walking and gardening.

Yoga is great for flexibility but also for relaxation and it can really help with your mental health.


The section Michael did with Curtis about snoring hit home for me. Like Michel, I used to snore badly, waking myself up numerous times a night because of the noise, I lost weight and don’t snore anywhere near as badly now!

He had asked Curtis to record himself while he slept for the first 10 days. And yes, not surprisingly, Curtis snores. I have a feeling that Curtis will be asked to record himself again towards the end to see if there is an improvement.

Obstructive Sleep Apnoea is where you stop breathing when you are asleep and 1.5 million people in the UK suffer with it but 85% of cases are not diagnosed.

Sleep is important for lots of reasons. Adequate sleep is important for weight control, and we need decent sleep for mental well-being as well as giving the body a chance to recoup energy.

People who snore are more likely to suffer with sleep apnoea. Quite often it’s down to neck size and excess fat around that area, although genetics and age also have a lot to do with it. For women, a neck size of 16” or more is an issue. For men, it’s 17”.


Michael had got loved ones of the volunteers to record videos of support for them, which was a nice touch. Great to have someone close telling you they are proud of you or that they know you can do it. It can really help you keep going.

Weighing In

The volunteers were weighed this week, but neither they, nor viewers got to see the results.

I think it would be more helpful to see results week-to-week. If you were considering a diet like this you would want to understand how the weight loss happens and where it comes from.

Nest week, Michael says he wants to help his volunteers change their relationship with food and, of course, there will be the big weight reveal.

Episode Three Review

This was the last episode for Michael Mosley’s Lose a Stone in 21 Days and we finally get to know how much weight the volunteers lost.

The five volunteers spent 3 weeks on 800-1000 calorie diets, low carb enough to put them into ketosis. They were also encouraged to get plenty of exercise.

Some of the group had really struggled with the portion sizes over the 21 days, which had to be very small to keep within the calorie restriction, and a few had suffered with dizziness and being ‘hangry’. Michael said he wanted to try and help his five volunteers stick to eating less and moving more and said he would stay in touch with the group in the coming months.

Celebrations and Tough Choices

Four of the group members found themselves having to make difficult choices as real-life situations caught up with them.

  • Adrian managed to abstain from birthday cake on his son’s birthday
  • Tracy drank only water and took her own food when meeting up with friends at the pub
  • Sharika worried about what to eat on a picnic with her friends but managed to resist temptation
  • Katie resisted the popcorn and sweets on a family movie night

With weigh-in day looming (and cameras rolling) all stuck to the rules.


Michael did say that mindfulness can really help when you are dieting. Both Tracy and Sharika feel that snacking through boredom was a problem for them – the mindless munching while watching TV.

Being mindful of what you are actually eating and taking the time to enjoy it without any distractions can help you feel satisfied with less food and can help reduce stress, therefore, reduce comfort eating. Check out what PT and Life Coach, Christina Neal has to say about mindful eating.

Make Your Choice

Michael hit the streets again. This time is was with chocolate, fruit and veg. He was offering passers-by the choice between the chocolate or the fruit and veg. No real surprises here when most people opted for the chocolate. Michael spoke to a neurologist about why people would choose the chocolate most of the time.

Basically, it’s down to the brain and dopamine. The brain has learned that eating chocolate releases dopamine and make it feel good. So, when faced with a choice, the brain wants what will be pleasurable – the chocolate.

Following Michael’s diet means no chocolate at all. I think I could manage that for three weeks but, it’s not something I would want to continue for the rest of my life. Just like celebrating or having lunch with family and friends, I wouldn’t be prepared to sacrifice it. Although I love fruit and veg, chocolate has a place in my diet too.

The Results

After three weeks of eating 800 calories, you would expect the volunteers to have lost weight. And they all had. In fact, they had lost over 5 stone between them, as well as 21” in total from their waists. They also all improved on their health scores. This was especially important to Katie, she had been pre-diabetic before the diet, whose blood sugar levels were back to normal. 

  • Tracey – lost 7” and 9lbs
  • Adrian – lost 4” and 13lbs
  • Sharika – lost 4” and a stone
  • Curtis – lost 4” (and an inch from his neck) and 1 stone 10lbs
  • Katie – 5” and 1 stone 2lbs

Overall the volunteers achieved some great results and a big kickstart to their weight loss. Well done to them, as we saw throughout the episodes, it wasn't always easy.

Since Michael will be staying in touch with the group, hopefully he'll be able to help them transition to a healthier, lower calorie, way of eating they can keep going for life.

How to Lose a Stone

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