I have to confess - I am really not into diets. I actually truly hate them. I believe in balanced nutrition and listening to your body´s needs. I have also been a (not so dogmatic) vegan for three years and was very happy with it. Being vegan brought a lot of new food discoveries and made me feel lighter and younger. So no complains at all.
Then I learned about the cream diet - yes, 10 days of whipped cream and crème fraiche/sour crème - from a very lean former professional triathlete. He was quite convincing and claimed that it was by far the best way to stimulate fat metabolism and to get to your racing weight (he promised up to 1kg of weight loss per day, provided one kept serious training load). I thought he was nuts, the diet was disgusting, anti-vegan and over the top extreme – but it made me think.
Fact is, highly trained endurance athletes are using both carbohydrate and fat metabolism to fuel their performance, both in racing and in training. They have highly developed fat burning capacity and trained their body to use stored fat effectively, even at race conditions. This is a huge advantage in endurance sports, since glycogen reserves get depleted fast and food intake capacity is limited: your digestive system cannot absorb more than, at the very high end, 80-90grams of carbs per hour, which is 320-360 Kcal, while you might be burning up to 1000 Kcal/per hour, thus accumulating energy deficit over time. If you don’t take any nutrition and if your body does not know how to use fat as fuel, the game (i.e the race) is over for you in two hours.
In order to go long, you need all the extra energy you can get and if you can access your fat depots, you can perform for a very long time without significant performance deterioration - we all, even the leanest among us, have enough fat to run several hundred miles on it.
Now back to the cream diet. Its logic is therefore very simple: you feed your system only fat, so it has no choice but to learn how to effectively use it as fuel! It will burn the fat you eat and it will burn the fat you so carefully stored, just in case you need to survive a winter in Siberian forest… One condition: you have to stay active, so that your body learns to burn fat also under stress, with elevated heart rates, and it learns to use it efficiently too.
For a more scientific explanation, we will have to revert to Krebs cycle. It is the system of energy metabolism in our bodies, a series of chemical reactions to produce energy molecules ATP - adenosine triphosphate, by oxidising carbohydrates, fats and proteins. Simply put, everything you eat gets broken down to glucose (and amino-acids, vitamins, etc). Glucose is our fuel and it means survival. The straightforward way to derive glucose is to oxidise carbohydrates. This explains why simple sugars contained abundantly in such things as Coca-Cola “get into your blood” right away and you feel a surge of energy immediately – it is a short cut for the body to make glucose out of simple sugar. And it gets truly addicted to it too. Whereas using fat for glucose metabolism takes longer and is a much less energy efficient process for the body. Unless it learns how to do it.
This learning takes some time, so you will most likely suffer a bit for the first two days on the cream diet. You will experience sugar cravings and feel low on energy – well, a bit like a (sugar) junkie. This is normal - your body wants a shortcut in form of sugar. You will have to deprive it from getting it – go on sugar rehab - so that your body has to get to stored fat to fuel your life.
On day 3 or 4 you will feel better – you will most probably have lost around 2kg and a cm or two around your waist. Do measure your waist, chest, thigh and arm circumferences – these are the fat depot areas and they will start melting, like polar ice caps… Provided you train like you did before – but now you take only water with you on your rides and runs (and maybe one emergency gel) – you will be surprised how long you can actually go without eating, snacking or drinking sugary drinks. Four hours on the bike with some 2000 altitude meters or 2 hours run – no problem! You will actually notice that it is easier to climb and to run hills now (recall, it is all about “power to weight” ratio when we go vertical…). This was also my experience. By day 9 or 10 you will probably be 4 to 5kgs (or more) lighter and your body will be way more energy efficient.
You will become fat-adapted. A lean, mean racing machine!
Getting off this diet is easy – have a cake with a lot of cream! And keep several “low carb” training days a week to maintain your newly acquired fat burning capacity. Train fasted in the morning – no breakfast and no or a small protein & fat dinner the night before. This works also if you don’t exercise – skip dinner and breakfast and you will have fasted (and burned fat) for almost 24hrs – this is how monks and ballerinas do it.
Enjoy your cream!
(Note for vegans: Cream is dairy. Not vegan. BUT - if you secretly like cream but did not have it in three years, I guess this diet will be a bit easier for you. It becomes almost a decadent experience to have a bowl of cream for breakfast... lunch... and dinner..).