Low carb brownies
Conventional wisdom argues that fat makes you fat and you should eat less of it and then you won't be fat anymore. Right?
Actually, not quite.
We are facing a paradigm shift in nutrition science and it is increasingly widely acknowledged that fats are not to blame for the fact that more than 2/3 of us are overweight, carbohydrates are.
Your body can store energy in 3 ways:
1kg of fat stores about 7700 calories of energy, so on average we each have many tens or even hundreds of thousands of calories stored up on our hips and waist. Some have in excess of a million (e.g. a 150kg man). In fact, if we assume that you burn roughly 700 calories in a 1 hour jog, that means our 150kg man holding 1,000,000 calories round his waist would have to run for 8 hours continuously for 3 months and not eat anything extra, just to lose half of that fat. Keep on running!
To lose weight, we of course have to reduce those stores of fat. Now, insulin is the hormone of plenty in the body, and amongst its multitude of effects it tells the body to store more fat and acts as a lever switching our bodies to preferentially use glucose as opposed to fat. Not ideal, this is the opposite to what we want if we want to lose weight!
Now consider this, humans evolved for and are built for a life of scarcity. In hunter gatherer times (i.e. 99% of the time homo sapiens have walked the earth), we would have lived a life of fasting and feasting cycles, where days of fasting (aside from a few berries here and there) would be punctuated irregularly with large protein feasts. There certainly wouldn't have been any of these thrice daily, solo gorges on carb heavy meals meant for a family of 4. Romans used to eat 1 meal a day and it wasn't until the 18th century that 3 square meals a day became the norm.
It certainly wasn't until the birth of fast food and on demand donuts over the past century that we have been able to dump what is essentially spoons and spoons of pure sugar into our blood, on demand, day after day. The effect this has, is to massively spike insulin levels, which as we mentioned earlier, causes us to build up bigger and bigger fat stores. Not only does this permanent state of high insulin make us fat, it also gives us diabetes and is thought to play a role in a host of other chronic diseases too.
Now here is the really key point.
Insulin levels are spiked by carbohydrate intake. Fat and protein do not raise insulin levels.
That's not just all those cookies and puddings, it's all that pasta, rice and bread as well.
So, given all of that, doesn't minimising insulin levels by cutting down on carbohydrate intake seem like a reasonable idea? Not only would this reverse the process of storing fat, but it would also switch that lever in our body to force preferential burning of fat and decrease our risk of diabetes.
This is where the ketogenic diet comes out to play.
The ketogenic diet turns conventional wisdom on its head by increasing fats to >65% of your daily calorie intake, reducing carbs to <40g a day and leaving the rest to protein. That means no pasta, bread, rice or sugar and limited amounts of fruit. But as much meat, veg, salad, eggs and cheese as you like. Following this diet and drastically reducing your carbohydrate intake puts your body into a special low insulin state whereby you are forced to use up fat stores at an unprecedented rate. But it's not just this that makes the keto diet special, there is another magic trick the keto diet has up its sleeve.
It produces ketone bodies. It does this because your brain can't use fat or protein to function, and so it converts fat stores into two specific brain fuel molecules: beta-hydroxybutyrate and acetoacetate. In addition to fuelling the brain, these two are at the centre of a lot of hot research into a multitude of other effects which I'll discuss in a minute.
First, does the keto diet work?
Well a meta-analysis in the British journal of nutrition analysed 13 studies covering 1577 people and found that those eating less than 50g of carbohydrates a day lost 1kg more weight than those on a conventional low fat diet.
Building upon that, this systematic review in the Lancet looked at 53 studies covering over 68,000 participants and found that low carb diets led to 1.15kg more weight loss than low fat diets.
Whilst that's impressive, most of these studies didn't use actual keto diets, they used low carb diets i.e. less than 50-75g carbs a day as opposed to the 20-30g necessary to induce ketosis. Strict keto diet protocols have shown even greater effects of up to 7.2% reductions in body mass. See here and here.
As well as ketogenesis (the production of ketone bodies) promoting weight loss by flicking a switch to promote higher fat utilisation and inhibiting fat storage, multiple studies (here, here, here and here) have also shown that the keto diet (specifically the presence of these ketone bodies), can reduce appetite by up to a 1/3, which will also contribute to weight loss.
One concern some have, is that eating all that fat will send cholesterol and blood lipid levels into disarray, thus raising the risk of heart disease. However, all the evidence suggests that this isn't the case. In all of the studies above, lipid profiles actually showed a significant improvement, even when compared to the low fat diets.
Unsurprisingly, keto diets have dramatic effects on diabetics too. Insulin sensitivity improved by 75% in one study, and HbA1c levels (measure of long term blood sugar levels) were consistently decreased by the same amount even the most powerful of diabetic medications would achieve (7.5% down to 6.3 being a typical result) - here and here.
Now, what about those other magical effects of ketones I mentioned. Now the evidence here gets less convincing purely because the research just hasn't been done, but what evidence there is certainly looks like it has potential. The best review I've seen is here in nature.
Here, the evolution of the human brain including higher cortical functions are described as having been driven by a need to sustain performance in the fasted state. Ketone bodies, it explains, are not only able to provide energy to the brain, but they also stimulate the production of BDNF (brain derived neurotrophic factor) which plays a well-established role in synaptic plasticity and cellular stress resistance i.e. allowing your brain to form new connections and recover and cope with insults much more easily. e.g. the resilience of neurons to traumatic brain injury and electrochemical damage as shown here.
It is thought that the mediators of these effects are not only BDNF, but also other classic actors in the metabolic and longevity field such as mTOR and IGF-1. More detail on how ketogenesis interacts with these here, here and here.
Our aforementioned BDNF has for a while been purported to be very important in depression and other mood disorders, via the neurotrophic hypothesis in which it is argued that depression results from reduced BDNF and thus reduced neurogenesis, particularly in the hippocampus.
It is not much of a leap then, to consider the potential of the ketogenic diet on mood disorders via this same mechanism, as has been discussed and, to a fairly modest level as yet, studied here and here.
The ketogenic diet is already an established treatment for refractory epilepsy and dystonic movement disorders as demonstrated in the NICE guidelines and this cochrane review.
But ketogenesis has also been claimed to have effects on other chronic brain disorders such as Alzheimer's and Parkinson's. The research here is at early stages and mainly in mouse models, so no conclusions can be drawn yet, but some initial trials in human patients with Alzheimer's disease do look promising. For example, in this one, 23 individuals with mild cognitive impairment (a dementia precursor) showed improved memory compared to those on a normal high carb diet and the effects were correlated to ketone levels and not calorie intake.
And these two (1, 2) show preliminary evidence for the diet's use in humans with Alzheimer's. In fact, this ketosis inducing compound is already approved for use in Alzheimer's in the US.
More tenuous now, but early research in mouse models of ALS (motor neuron disease) also suggests a significant effect of the keto diet. And in mouse models of brain tumours, it is able to reduce tumour growth and enhances the efficacy of radiation and chemotherapy.
There are currently 11 trials ongoing, assessing the efficacy of ketogenic diets as adjuvant therapy in human cancer patients as summarised here. Preliminary reports suggest that of those who manage to stick to the diet for 3 months, most showed improvement with a stable physical condition, tumour shrinkage or slowed tumour growth. The evidence is really not there yet however and it is too early to tell what the full effect is with any certainty. One major issue commonly reported is the ability of patients to stick to the diet, given the severity of their situation, so whilst not unsafe and, when successfully followed shows no self-reported reductions in quality of life, this may be a limiting factor in its use.
Even in autism, this study shows that of 23 children with autism trialled on a keto diet, 2 improved enough to be moved into mainstream education while a further 7 more showed significant benefits (1, 2). This is supported by this meta analysis.
And finally, there are even suggested effects of reducing carbohydrate consumption on acne, albeit no actual studies of the ketogenic diet itself (1, 2, 3). And in 23 women with PCOS (polycystic ovarian syndrome), the ketogenic diet had a significant impact on their symptoms and hormone profiles and two even managed to become pregnant despite having previous difficulty (obviously we can't attribute that to the diet with such sparse evidence, but we can hypothesise!)
So with that, here are some tools to get you started!
Two good informational websites here and here. Tim Ferriss' slow carb diet is essentially the same thing and there are a multitude of resources out there for that.
The best low carb brownie recipe.
The best low carb bread recipe.
A great cookbook.
And a blood ketone meter to check your levels.