Juliet Blank
Associate EditorThe Cambridge Diet – officially called The 1:1 Diet by Cambridge Weight Plan – is popular with people looking to lose a lot of weight quickly. Find how it works, what the different Steps are all about, and whether it's safe to do when you’re trying to conceive (TTC), pregnant or breastfeeding.
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What is The Cambridge Diet?
The Cambridge Diet is a rapid weight loss programme developed in the '60s by Dr Alan Howard at Cambridge University (hence the name). These days, it's officially called The 1:1 Diet by Cambridge Weight Plan .
The main idea of the diet is to replace much (or even all) of your normal food with meal-replacement products such as soups, shakes and bars, which you have to buy.
Depending on how much weight you want to lose, there’s a choice of six diet plans known as 'Steps'.
These range from a very low calorie plan (sometimes known as the ‘Sole Source’ plan, where you only eat official 1:1 products) through to 1,500 calories (the ‘Maintenance’ plan where you eat low calorie meals alongside the products.)
How does The Cambridge Diet work?
The Cambridge Diet (or 1:1 diet) works in part by forcing your body into a state of ‘ketosis’. This is basically where your body isn’t getting enough calories from carbohydrates so it resorts to burning your own fat stores instead.
This is similar to the Keto diet .
The plan is quite extreme and you can’t follow it on your own.
Instead you need to sign up with a 1:1 Cambridge Weight Plan consultant who will give you one-to-one advice and support on what to eat.
You're also advised to check with your doctor before starting the diet plan.
The 1:1 consultant will weigh and measure you to decide which programme is best for you and help you achieve your weight loss goals.
The Cambridge Diet: what are the different Steps?
There are six different diet stages, known as Steps, that tell you how many calories and what you can eat each day.
Your 1:1 consultant will help advise you which Step to start on – for example, you can start from Step 3 if you don't want the really low calorie intake in Steps 1 and 2. You can also move from Step to Step whenever you like.
Here's what each Step involves:
Cambridge Diet Step 1
Eat three or four 1:1 diet products and drink 2.25 litres of water a day.
On Step 1, you'll only be getting between 415 and 554 calories a day in total.
You can only do Step 1 for a maximum of 12 weeks. This step is designed to kick-start your weight loss, and is also great if you just want to lose a few pounds for a one-off special event. But it's not a good long-term option, as you won't be getting all the calories and nutrients you need.
Cambridge Diet Step 2
Eat three 1:1 diet products and one healthy meal of your choice – Cambridge Weight Plan offer low-cal 'Step Up Meals', or you can make your own. You should continue drinking the same amount of water and you can also have tea and coffee.
On Step 2, you'll be getting roughly 800 calories a day in total.
This step aims to ease you back in to eating regular foods, though it's still a very low-calorie option.
Cambridge Diet Step 3
Eat two 1:1 diet products, one healthy breakfast, light lunch, and a low-calorie dinner . As before, you need to drink a minimum of 2.25 litres of water.
On Step 3, you'll be getting roughly 1,000 calories a day in total.
The 1:1 diet products can include their healthy meals (such as beef casserole and vegetable soup), or their tasty snacks (such as cherry bakewell flavour bar).
Cambridge Diet Step 4
Eat two 1:1 diet products, one healthy breakfast, light lunch, and low-calorie dinner, plus a couple of healthy snacks. Keep it up with the 2.25 litres of water, too.
On Step 4, you'll be getting roughly 1,200 calories a day in total.
Step 4 of the plan is ideal for people with more active lives, who may need a few more calories to help them get through the day. The extra healthy snacks will give you the boost you need, plus a chance to get a wider variety of nutrients in your diet.
Cambridge Diet Step 5
Eat one 1:1 diet product, one healthy breakfast, one light lunch and one low-calorie dinner. Continue to drink at least 2.25 litres of water.
On Step 5, you'll be getting roughly 1,500 calories a day in total.
This is still a low calorie diet, but you're much closer to eating normal food now. This step helps you get used to healthy eating without relying so much on the 1:1 diet products.
Cambridge Diet Step 6
This is the maintenance stage , where you are now eating to maintain your weight loss and make sure you don't put the weight back on again.
After each stage, your 1:1 diet consultant will advise you on how to start slowly introducing regular foods again. They'll help you work out the best step for you, and give you plenty of motivation to stay on track.
Is The Cambridge Diet right for me?
The first thing you should do is work out your BMI to see if you need to lose weight.
The 1:1 diet website has a BMI calculator you can use.
If your BMI is over 25, you are classed as overweight and can do The 1:1 diet. However, you are advised to talk to your GP before starting any weight loss programme. People who are underweight shouldn't do the Cambridge Diet.
Cambridge Diet Plan states that it's not suitable for you if:
- Your BMI is below 20
- You have an eating disorder
- You are under 14 years of age
- You have had a heart attack or stroke in the past three months
- You are taking prescribed monoamine oxidase inhibitor medication
- You are taking anti-obesity medication
- You are a substance misuser or dependent on alcohol
- You are pregnant or breastfeeding, or have given birth in the past 3 months
Linia Patel, a dietitian and British Dietetic Association spokeswoman says:
'There are a few different plans within The 1:1 diet. However, overall The 1-1 diet isn’t sustainable. If you follow the very low calorie diet (500 calories per day for example) you risk losing precious muscle mass.'
How much weight will I lose on The Cambridge Diet?
Your weight loss is likely to be quite quick as the number of calories you are eating as so restricted.
This is especially true in Step 1 when you're having as little as around a quarter of the recommended daily calorie intake for women.
The 1:1 diet 'Woman of the Year' for 2021 was Rachael Walkingshaw-McGuinness who lost 9st 1.5lb on the plan, while another dieter lost over 12 stone.
It's worth noting that the NHS recommends slower weight loss saying you should:
'Aim to lose weight at around 0.5kg to 1kg a week (1lb to 2lb)'
Will The Cambridge Diet affect my fertility?
Following a healthy, balanced diet is recommended if you’re trying to get pregnant.
As such, The Cambridge Diet might not be right for you – especially if you’re on the very low-calorie plan as you may not be getting enough calorie and nutrients your body needs.
Dietician Linia says:
‘The 1,500 kcal per day plan may be a way to kick start weight loss before you conceive. However, I would recommend that you work with a dietitian or registered nutritionist to ensure effective weight loss and sustainability in the long term.
‘Using it as a starting point, you can then work with a dietitian to start incorporating more solid food.’
According to Cambridge Weight Plan, losing weight quickly can affect your periods, too. On its website it explains:
‘In most cases the menstrual cycle remains unchanged but for some women breakthrough bleeding or heavier periods may occur. Others may find that their periods stop for a while.
‘Fertility may also be affected and unexpected pregnancies have been known to occur, therefore if you have been trying unsuccessfully to become pregnant, you need to be aware that during and after weight loss, fertility may increase.’
Can I do The Cambridge Diet if I’m pregnant?
No, you won’t be allowed to sign up for The 1:1 diet if you’re:
- pregnant
- breastfeeding
- have given birth in the last three months
During these times, your body needs more calories than the 1:1 diet can provide.
Can I do The Cambridge Diet if I’m breastfeeding?
No, as above, the diet is not suitable for breastfeeding women.
Christine says:
‘Pregnant and lactating women require increased levels of protein and energy, and are advised to follow a diet rich in lean protein, whole grains, fresh fruit and vegetables.’
What are the side-effects of The Cambridge Diet?
Eating so few calories can have a number of physical side effects. These can include:
- bad breath
- feeling cold, especially your hands and feet
- headaches
- a dry mouth
- tiredness and/or insomnia
- dizziness
- changes to your periods (heavier, spotting or stopping altogether)
- constipation (from cutting down your fibre)
- diarrhoea (from increased mineral consumption)
- hair loss
These side-effects can happen with any very low calorie diet. If you're experiencing side-effects of weight loss, chat to your GP. You should also always check with your GP before starting a strict diet if you have any kind of health condition.
What are The Cambridge Diet products?
If you follow the diet plan, a lot (or all) of what you eat will be 1:1 diet products .
These meal replacements are full of the vitamins and minerals you need to stay healthy and include:
- low-calorie shakes
- soups
- smoothies
- porridge
- snack bites
- meal replacement bars
- meal replacements, such as spaghetti bolognese flavour pasta or chicken tikka style curry
-
Step Up meals, such as chicken tagine with chickpeas or smoky three bean and lentil casserole
Keeping a food diary or using a diet planner can help keep you focussed. We like this planner that comes with a calorie counter, mood tracker, plus stickers to help you track your progress. See more details here at Amazon.
How much does The 1:1 diet cost?
It costs around £58.38 a week, which is based on three products a day and a weekly one-to-one session with your 1:1 diet consultant.
The 1:1 website does say, 'Prices vary from Consultant to Consultant, but on average, you’ll only pay around £2.78 for a meal.
Cambridge Diet reviews
Here's what Netmums' Forum has to say about the Cambridge Diet:
'I did Cambridge. I lost 5 stone in 5 months. It's hard and s little pricey but it definitely works. Just remember to drink plenty of water!' – Maria A A
'I have just completed my fourth day. Not feeling hungry but finding the soups and meals a bit salty... just trying to keep focused on the end goal!' – NikNak50
'I have fallen off a couple of times (weekends hardest) but have managed to lose a stone so far.' – NikNak50
'I do know someone who did the Cambridge diet and know first hand that it is hard going and afterwards all the weight creeps back because you haven't learned ways of eating differently. You simply replace 2 meals a day with a milk shake type drink. You have to buy their own snacks which also proves expensive. I think if you did try this, lost weight and then had it all come back on then you would feel incredibly disappointed and not much better so I would go for exercise and a healthy eating plan which will help you feel good.' – Anonymous
'On Cambridge plan you have a mixture of 4 products a day on step 1 and you can have food once a day if you choose and skimmed milk, I find it easier to stick to than regular diets and have tried lots, the down side is the expense but if like me you spend way too much on every supermarket visit plus at the garage local shop etc on snacks it works out a lot cheaper. I have just started my week 3 of cambridge plan and have started eating eating meals. Mentally I feel 100% better and I am no stranger to feeling very down and or stressed, food really effects my emotions! (...) The good thing about the plan is you are getting all the nutrients you need [...] and you find out your food triggers, like being unhappy, angry, bored and get a chance to process them triggers unlike sw (Slimming World) or ww (Weight Watchers) where you can eat lots of free foods so you tend to eat way too many of them free foods never learning about yourself, I also found I was constantly hungry on other diets, where as I am not on this one, though that is not to say there are not hungry days and days when I could stuff my face but that is the reality whichever diet I am on or not.' – Anonymous
'I've not recently started it but have done it before, I lasted 2.5 weeks as I found it soooo hard! However I did lose 24lbs in that time. It works amazingly and if you can get through the first 4 days you will honestly not feel hunger anymore! My issue was I had a treat night?! The food puts you right back to the beginning of the 4 day starve so I decided I'd rather eat a salad and lose the weight more slowly than live on shakes!' – Julie123
'I did the Cambridge Diet last year and lost 2.5 stone in 3 months! I'd done every other diet imaginable and this one definitely worked for me. It seems expensive to start but its actually cheaper than doing WW or all the others and because you lose the weight fast you don't have to keep paying out for meetings or over priced diet food. Once you get past the first 3 days you should not feel hungry anymore and then it is really plain sailing after that. The hard bit comes when you have to start eating food again!!' – Anonymous
'I'm on week 3 of the Cambridge diet and not doing too great to be honest! I'm on sole source and I have really good days, then I have horrible horrible days where I just want to eat ANYTHING! I've lost 1/2 a stone so far, am day 1 into week 3 so I'm really hoping to stay on track this week and would love to shed another 6lbs.' – Anonymous
'I have been on the Cambridge diet a few times now and can honesty say it's the best diet in the world. Bloody hard work... but amazing results. I went on it after i stopped breast feeding my son and within a few weeks i had lost so much weight. I was smaller than before I fell pregnant!! And ive always really struggled with my weight. Put it on so easily so could not believe it. First time ever I had been remotely slim. Even my OH was like..wow you look so slim. All i would say is... if you don't stick to it 100% then there is no point doing it. It doesnt work, even if you cheat a little. You really can have any snacks or nibbles. I would also recommend just having the soups and milkshakes as the other snacks they provide aren't worth it. Once you take a bite of real food it all goes out the window. Stick to the shakes and soups. The hardest days is the first 5 days... .if you can make it though these 5 days of complete HEL... then you've cracked it. It gets easier and easier from there and before you know it all desire to eat normal food goes. Its just those 5 days which is so so so hard. By the 5th day I was a complete mess and crying all the time. But after that it was great. Skinny Minny!!!! Also the more water you drink... the more weight you lose... so walk around with a giant bottle of water... take it everywhere and drink as much as you can. Also if you really are going to crack and theres nothing else you can do... and just need something... just have diet coke! It has no sugar in it.' – Anonymous
'I have been on this diet for 8 days now, and I have already lost 10 pounds. I don't feel hungry at all! Even though obviously I am tempted by food, but not enough for me to break down and lose control of the diet. It's much easier than I thought, and I find the more I lose the more determined I am to keep doing. Key things to do - drink LOTS of water, the more water you drink the more you lose. Try peppermint tea as well, that's really nice.' – Anonymous
'Sorry all you ladies that are on the Cambridge Diet, but you will be on it again and again, yes it works but any starvation type diet will work. it is a fast fix but can be very detrimental in the "long term". Sensible eating is the only way to go and to do it slowly, no-one gained their "stones" over night so why expect to shift it overnight. Cambridge diet does give you the vitamins etc' that you need unlike some of the other quick fixes, but unless you have loads of money and stay on off on off on off it forever it will not cure you of your weight problem. All the best anyway XXXX' – Anonymous
'Just wanted to give a balanced opinion really. I've lost a lot of weight. Some doing slimming world, some doing Cambridge & I've maintained my weight loss for some time now. I feel it's quite important to point out that a lot of people regain their weight,(something like 80% I believe) this isn't just a symptom of the Cambridge diet. In no way am I an advocate of the Cambridge, but I do believe it has it's place in the weight loss market. It's an extreme diet for people with an extreme weight problem. It's not really for people that want to shift half a stone. For me,it was the end of the road, a last resort. I now have a bmi from 40 down to 23 Im eating a balanced healthy diet and happily maintaining my weight loss. Cambridge, If guided by an experienced helpful councillor can be a really good weight loss program, as can Slimming World, Weight Watchers etc. The Cambridge diet generally doesn't get followed properly and that is why people regain their weight.' – Anonymous
Have you tried The Cambridge Diet? Chat about it in our forum below, or check out our articles for more slimming tips:
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