Tired of feeling tired, Victoria Woodhall tried a radical 10-day eating plan to boost her energy levels. Could this be possible without a single carb? Here's what she ate - and the surprising things she discovered

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I always swore I’d never do the high-fat ‘ketogenic’ diet . I remember with slight revulsion the noughties, when people were dropping half their bodyweight on Atkins, the first keto plan to hit the mainstream and which consisted mainly of fat and protein. They’d bring their Tupperware boxes full of steak, sausages, bacon, eggs, and butter, have coffee laced with cream and worry about their ‘keto breath’. Just thinking about it was enough to bung me up. I didn’t have weight to lose, so why 20 years on, did I spend 10 days on a high-fat diet with virtually not a single carb passing my lips?

Like many of my generation, I grew up believing the line that 'fat makes you fat’. So-called ‘healthy’ eating advice, which we now know to be flawed, steered us away from supposedly artery-clogging animal fats, towards (often highly-processed) vegetable oils and low-fat starchy carbs. At university, I lived on low-fat fruit yoghurts, which were rammed with artificial sweetener and bulking agents (not that we knew or cared, we only ever looked at the calorie count), my toast was always spread with low-fat margarine and milk was always skimmed. Glucose tablets were a favourite during exams. But as my weight was healthy, it never occurred to me that my diet was not. The idea of eating more fat went against everything I’d been told.

These days we know so much more - healthy fat is having a rightful moment to the extent of causing avocado and almond shortages. There are busy #keto discussions on Instagram and celebrities are happy to discuss how it keeps them in shape. Actress (and diabetic)  Halle Berry  revealed on the platform that she had been on it for years as a lifestyle choice and that it had been "largely responsible for slowing down my aging process." It's well known that sugar causes skin ageing .

While my diet is now significantly better than it was in my twenties, it's still quite carb-heavy and I’m often tired and slave to energy slumps. I mentioned this to Zana Morris, who runs the London’s Library Gym, known for its sculpting 15-minute high-intensity weight training workouts and also for its 12-Day High Fat Diet. Friends and colleagues who had done the diet had shifted half a stone easily - GTG's own  Sarah Vine called it The One -  but they'd always told me how ‘hardcore’ it was. Others objected to having to weigh their broccoli. Why would I want to put myself through it if I had no weight to lose?

Fat makes you feel fuller for longer so you don’t get those energy dips. SUGAR IS CHEAP FUEL

Zana urged me to try the HFD to see what happened to my energy levels when I switched from using carbs as fuel to burning fat for energy (ketosis). This, she was confident, could take the blood sugar swings and slumps out of my life. “Fat contains double the calories, which everybody used to think was a bad thing, but it’s double the energy,” she explains. Her team always notices when she herself does the HFD, because she works at full throttle and is fizzing with ideas.

“Fat makes you feel fuller for longer so you don’t get those energy dips. It is much more powerful fuel than sugar. Sugar is like a cheap fuel which does the trick immediately but doesn’t really have any significant health benefits. Plus, there are the fat-soluble vitamins, which are all those we seem to be lacking: the As, Ds, Es – they all need fat. Your brain fuels primarily from fat rather than sugars and if your fat levels get too low, your hormones don’t function properly. And it’s the only food group that doesn’t cause a release of insulin.”

Ah, insulin, the hormone that we’re all spiking too often because we simply consume too many sugars; weight around the middle is a tell-tale sign of spiralling insulin. When I spoke to Dr Michael Mosley, author of the Fast Diet, he told me also that “insulin is not only a fat storage hormone but a cell growth accelerator strongly linked with a number of cancers.” There’s every reason to keep our levels stable. This was another compelling reason for me give the diet a go.

Bulletproof cacao and The High Fat Diet book

In the last six months, I’d been making baby steps in that direction anyway, swapping my Bircher Muesli breakfast, which always made me hungry mid-morning, for ‘bulletproof’ cacao - my own coffee-avoider’s version of Bulletproof Coffee , comprising a couple of tablespoons of coconut oil with either organic raw cacao powder or matcha. This was essentially a high fat carb-free meal which kept me full til noon and my energy levels even. I had been doing high fat for a chunk of the day anyway and liked how it felt.

So what could I eat?

On the HFD, I could keep my bulletproof breakfast (or choose eggs and/or smoked salmon and cream cheese) but I would have to add a bit of protein powder as the diet works on strict ratios of fat and protein. For the remaining two meals, I could eat 85g of a high-fat food (ie one that’s approximately 70 per cent fat) such as a whole avocado or high-fat cheese such as half a tub of Philadelphia or mascarpone or a large handful of walnuts or pumpkin seeds; I'd need to add 80-120g of a high protein food (a chicken or salmon fillet, two to three eggs or medium fat cheeses which count as protein - a ball of mozzarella, fried halloumi etc) and 40g of any green or white veg. Veg of any other colour are too starchy, so no red peppers, carrots etc. If I was hungry, I could have a protein shake made with a full carton of coconut cream rather than milk (too carby). I could drink water, black tea or coffee with cream. “You should never feel hungry,” said Zana. "If you do, then you are not eating enough fat”.

She had one key caveat though: “It’s the fastest way to gain weight if you do it wrong. You gain weight fast if you mix fat with carbs as then you are on a mega calorie plan. Carbs are a cheaper faster fuel for your body, which then stops burning the fat and all that extra fat is just calories stored.” This is when cholesterol can become an issue as a high fat alone does not cause an increase in bad cholesterol, in fact, it lowers it, she explains. But the mixture of fat and carbs can be dangerous for cholesterol. “We monitor people closely on the High Fat Diet - we basically ask them lost of questions about what they are eating - and if they do cheat we take them off it.”

With that warning ringing in my ears, I set off to fill my trolley. In my basket I put salmon, tuna, eggs, chicken, leaf spinach, rocket, cucumber, sugar snap peas, mushrooms, pumpkin and sunflower seeds, parmesan and pine nuts, (homemade pesto is totally HFD) mozzarella, halloumi, cream cheese, olive oil, apple cider vinegar, coconut oil, coconut cream, raw cacao, basil, mint and coriander. Didn't sound too bad!

Halloumi and avocado salad

What I learned on the High Fat Diet

1. You’re in a calorie vortex.
It’s best not to count them. You can easily be eating 2,500 calories a day on the High Fat Diet and still not gain weight. Why exactly is still a mystery; one theory is that, because it takes more energy to create fuel from protein and fat than from glucose, you burn more in the process. Also, you are keeping insulin, the fat storage hormone out of play. In fat-burning mode, you are busy burning up your body's excess fat stores and shedding the weight you don't want.  I’m pretty sure I ate more than 2,500 calories as I had three meals a day (some people feel full on just two) and a snack. Zana explained that because I was already quite lean, I didn't have much body fat to burn, so it was important to eat enough fuel.

2. Not all calories are equal.
Macros have very different metabolic effects. Combining fats and carbs is a weight gain hazard (think moreish Dairy Milk). Combining fats and proteins (think not-so-moreish cheese omelette) can help you lose weight and the difference is that the first unleashes the fat-storage hormone insulin, the second doesn’t. “Protein breaks down into amino acids and sugars – so lean protein (think cod) does, as it digests quickly and there is a sugar hit to the bloodstream; however salmon – due to the fat – releases less. Salmon with avocado, even less. Fat slows down the breakdown digestion of the protein so there’s less of an insulin ‘surge’,” Zana tells me.

3. You feel full in a different way.
I didn’t get that usual heavy feeling after a meal, despite consuming vats of cream cheese, or that post-meal slump, which would ordinarily have had me reaching for the cake. I simply felt the absence of hunger and could power on without a sweet snack (although simply out of habit I missed my sugar fix).

4. Your wee is clearer.
Even first thing in the morning, it’s less cloudy and (TMI alert) less yeasty-smelling. Why? I am guessing that as urine is used to measure the sugar in your system (as anyone who’s ever peed in a pot at their GP will know) less sugar will change what comes out. I was starting to feel cleaner on the inside as if my body was working more efficiently. I also was more able to tell when I was thirsty and drank more water.

5. Eating is an event. No grabbed food al-desko. Because I wasn’t picking or snacking I looked forward to my prepared meals and they became an event to be savoured without a screen.

Mozzarella salad

6. 'Brown food' Atkins-style keto meals are a thing of the past.
My keto plate was mostly green thanks to daily avocado, pumpkin seeds, sugar snap peas, green beans and salad. These ‘above ground veg’ contain traces or carbs, so you still have to make sure to stick to your 40g, which is a lot of salad but only a small handful of cooked broccoli.

7. Eating out is a doddle.
Everywhere (unless you’re going vegan, in which case this plan is not for you) does eggs, chicken, steak or fish, olive oil and a side of avocado or high-fat cheese. I was caught out by a set menu at a birthday party. I skipped the cheese course because it didn’t arrive until 11pm and I wanted to be able to sleep. But it meant I hadn’t had my fat quota and therefore my fuel. The next day I could barely get out of bed and felt like someone had taken my batteries out. It took the entire morning to feel normal again because fat takes longer to convert to glucose than sugar.

8. You learn the difference between genuine hunger and cravings.  
Real hunger, as I discovered is pretty unpleasant and your body lets you know you need to eat. “The beauty of when you stabilise insulin,” says Zana, “is you eat according to real hunger. When the insulin is spiralling, it’s the hormone ghrelin screaming at you, which causes the cravings.”

9. You poo less.
Although the diet had more fibre than I expected with the green veg and nuts, I did get constipated. I took Pukka’s Ayurvedic Triphala tablets in the morning, to shove things along. Zana advised that calcium from all that dairy and eggs can bung you up and gave me magnesium to relax my muscles, which helped. But she also said that you are simply burning up much of what you eat and there’s less fibre, so there’s less to come out the other end.

10. Unexpected things start to taste sweet.
Pine nuts -who knew? And coconut cream is practically pudding. A spoonful of two after lunch can satisfy that sweet craving - ditto Yogi chocolate tea, liquorice tea, a shake of cinnamon in my morning cacao. Your taste buds become sharpened.

Chocolate mousse

11. Necessity (or desperation) is the mother of invention.
I improvised a dessert of mint chocolate mousse from coconut cream, a scoop of Library Gym chocolate protein powder (not so sweet that it takes you out of ketosis) and mint leaves and on a hot day, I put it in the ice cream maker. I was so pleased with myself, I could have sent it to Blue Peter.

12. It sculpts your belly - and your face.
Although I didn’t lose any weight, I lost inches of bloating and had a much trimmer stomach. Abs are definitely made in the kitchen. Zana reports that a well-known actress does the diet twice a year before a new stage show because she says it ‘sucks everything in’ especially on her face. Zana believes this is because carbs can also give some people puffiness.

13. You can’t eat the rainbow.
We all know that different coloured fruit and veg contain different antioxidants as well as feeding your gut bacteria and on this diet, you only eat greens and whites and so you forgo that variety, as well as the nutrients and fibre from grains and pulses. It’s a brief blitz, not an eating plan to live by.

14. There's that awful post-meal pang.
That’s you done for another few hours. No picking, no milk in your tea. Violins, please...

15. You gain time. 
There’s no point deliberating whether to neaten off the corners of that cake or quiche yet again. You are not constantly idling in front of the open fridge because there’s nothing in it for you til mealtimes. You realise how much of your day you spend thinking about food when insulin and ghrelin are constantly needling you. You have more energy generally, you're clear-headed and more productive.

16. You sleep better. 
Because nothing passes your lips after an evening meal, you’re not digesting that 10pm snack or feeling the sugar crash in the early hours after that last glass of wine - insulin can cause you to wake up after a few hours, says Zana. You put yourself to bed earlier because life without treats can get a bit dull.

17. You don’t have to be teetotal.
White spirits (vodka and gin) are allowed occasionally with soda and fresh lime. While not exactly delicious, it made feel less of a party pooper at my friend's birthday. Seedlip  non-alcoholic spirits are allowed as they don’t take you out of ketosis.

18. Your PMT isn’t as severe.
That’s what happened to me. In fact, you feel more on an even keel generally. Excess insulin can cause an imbalance in the body generally, says Zana.

19. There’s a massive disincentive to cheat.
The minute you eat a carb, fat-storing insulin can be triggered. And remember how much fat you are eating? You really don’t want to put all that on. However, eating enough fat with a carb can slow down the insulin release dramatically, says Zana, but there’s a fine line.  A sneaky glass of wine on an empty stomach can undo all your hard work but a square of dark chocolate after a meal may not. But in my experience, there no such thing as just one square. It's just not worth it.

20. Your breath doesn’t smell.
A complaint of old-style keto diets that may have been high in processed meats. Or maybe people were just too polite to say. I find tongue scraping helps. The presence of the greens, which do contain small amounts of carbs helps, says Zana, as you don’t go into the highest level of ketosis. This is when 'keto breath' can strike.

21. You eat according to your hunger.
That can be a novelty! If you don't feel hungry, it's because you're using your own fat stores. Many people, especially those with one to 14 pounds to lose, feel full on just two meals a day, Zana tells me, and those with more to lose might feel full on just one. I had the opposite problem. I had to remember to eat enough (at least three meals and snack) otherwise I'd be ravenous, as I had fewer fat reserves.

22. You can't pick and choose your food groups.
If you want to halve a meal you have to keep the proportion of fats to proteins, not just eat the chicken, say. Likewise, a snack should be a mini meal, not just one food group.

Salmon and walnut salad

23. You can’t under-eat or lose more weight than you need.
If your body needs fuel, it tells you in no uncertain terms - you simply can’t function, as I found when I didn't eat enough fat (see point 7). In my experience, it helps you find your natural weight. I neither gained nor lost, although my shape changed, because I lost bloating.

24. Brazil nuts are not as fatty as you think.
Even though they are held up as extremely fattening, they are not allowed on the HFD because they have too high a carb content. Same goes for cashews, almonds and all other nuts apart from macadamia nuts, pine nuts and walnuts. Not on the HFD? Enjoy!

25. You develop an eye for portion sizes 
On day three I stopped needing to weigh things and used handfuls and cups. The formula is very simple and you quickly become used to what 85g of high-fat food or 120g of protein looks like. If you get bored, there are recipes in Zana’s book . But I actually enjoyed the simplicity of it - it took the thinking out of meal prep.

26. High-fat meals are not cheap.
You’re eating one or even two salmon fillets a day, organic chicken, pine nuts, none of them cheap. But think of what you are saving on lattes and booze.

27. It removes the emotion from food.
Because there are no highs and lows, you start to appreciate food as fuel rather than reward or pick-me-up. On the flipside, mealtimes can become a bit functional and you’re not the easiest dinner guest. However, I was able to taste my food better and this stopped the diet from becoming dull. I loved the big portions.

28. Family meals are doable.
Because the diet is based on food cooked from scratch – essentially veg, protein and fat, you can easily make your own tweaks to a roast chicken dinner en famille. I was careful how I talked about the diet around my children, though, as I didn’t want them to think that anything they were eating was unhealthy, even if I was skipping it. I referred to the HFD not as a diet but as an eating plan ‘for work’.

29. Coming off the diet can be a flashpoint.
You need to be mindful not to eat anything like as much fat as you have been doing or you’ll put on weight.

30. Sugar is downright manipulative.
Going back, with glee to proper ice cream and my daughter's homemade brownies, I realised just how clever sugar is at drawing you in - no wonder they say it's as addictive as cocaine. Being wiser to its ways helped me to resist that second portion. I now try to keep my carbs mainly to the evening when I don’t mind feeling a bit more tired (in fact I welcome it)  and have added more protein to my lunch to keep me feeling full.

31. It’s an education.
Doing the High Fat Diet has given me a new appreciation of how our bodies function when we return to 'factory settings' - the way we were designed to fuel ourselves through famine and feast. It makes you realise too just how easy it is to mess that up and at a cost to our health. I've become better at eating in a way that keeps insulin stable (I eat higher fat at breakfast and lunch) which is both better for my energy and my health overall. I feel more alert and less of a carb slave. I'm not about to give up my glass of wine, mind you, but I know that a Pinot on an empty stomach will create an insulin surge - one with a meal, the French way, less so.

So would I do it again? Yes, a couple of times a year, as a reset, but I'm not about to embrace it as a lifestyle choice like Halle Berry - for one thing, I'm not organised enough. Plus, there is too rich a variety of good food out there and we know that the microbiome thrives on a rainbow and fibre-rich diet , which is vital for physical and mental balance. However, I do always now have insulin stability in mind when I eat.

32. This is not the sort of diet to embark on lightly or freestyle on.
Your food shop needs careful prepping and you need to stick to the plan religiously. I would not have done it without Zana’s careful supervision - there's always someone at The Library to call for advice. The book also gives chapter and verse on how to follow the plan and find out whether it’s for you. It’s not recommended if you have Type 1 Diabetes, are pregnant or breastfeeding. If you have heart disease, high cholesterol or high triglycerides you must consult your doctor first - good advice for anyone embarking on a drastic change in diet.

The High Fat Diet – How to Lose 10lbs in 14 Days by Zana Morris and Helen Foster £7.99

The Library Gym  12 Day programme, which includes nutrition consultations and training costs from £595. It is available at Notting Hill, Barnes and Wimpole Street, London.