Diet wars: Can you really eat fat and get lean?
There’s a food fight cooking…
In the red corner, we have the national nutrition guidelines, with its support crew of dietitians and most of the conservative medical and scientific community. They are the reigning public health champions. They are undefeated, but then they haven’t been seriously challenged. Until now. In the blue corner, we have a new challenger. He’s been around a while but till now he’s just been shadow boxing. For some reason he strikes fear in those around him. I present to you…..Fat.
We’ve been told for decades now that saturated fat is the major enemy in the battle against obesity and chronic disease. Reduce your fat intake and eat more carbs instead we’re told. Carbs are essential for human health we’re told. Eat less, move more we’re told and you’ll stay in shape. Here are the National Nutrition guideline for New Zealand.:
- Maintain a healthy body weight by eating well and by daily physical activity.*
- Eat well by including a variety of nutritious foods from each of the four major food groups each day:
- Eat plenty of vegetables and fruits.
- Eat plenty of breads and cereals, preferably wholegrain.
- Have milk and milk products in your diet, preferably reduced or low-fat options.
- Include lean meat, poultry, seafood, eggs or alternatives.
- Prepare foods or choose pre-prepared foods, drinks and snacks:
- with minimal added fat, especially saturated fat
- that are low in salt; if using salt, choose iodised salt
- with little added sugar; limit your intake of high-sugar foods.
- Drink plenty of liquids each day, especially water.
- If choosing to drink alcohol, limit your intake.
- Purchase, prepare, cook and store food to ensure food safety.
* At least 30 minutes of moderate intensity physical activity on most if not all days of the week and if possible add some vigorous exercise for extra health and fitness.
Yep, that’s the advice and what I have been preaching publicly for the last 15 years, and practicing privately for my whole adult life.
So what’s the problem? The guidelines seem sensible right? They’re evidence based, and the evidence is extensive right? Yes, sort of, and no.
Let’s deal with the Yes’s first:
Yes, there is extensive and compelling evidence that the type of diet described above is better for you than the Standard American Diet, henceforth known as the SAD :(. This evidence is from randomized controlled trials, detailed longitudinal studies, and correlational studies. There are plausible and known mechanisms for some of it, especially whole foods and meats. The important and convincing data around exercise and health is reflected in the guidelines too.
But that’s compared to the SAD. It’s like saying that because studies show that smoking filtered, low tar cigarettes results in better health, less lung cancer, stroke, and heart disease than smoking roll your own cigarettes, that we should all smoke low-tar cigarettes. Bogus logic.
The Sort Of’s
- Sort Of: The part about maintaining a healthy body weight is true – that is good for you. And eating healthily certainly is the way to do this. A low fat diet could make this possible but in the 18 randomized controlled trials to date, where low fat diets have been pitted against low carb high fat (LCHF) diets, there is no instance where the low fat diet has outperformed the LCHF diet. Weight loss and risk profiles, including lipids, are all better with the LCHF. It’s been a knockout in every fight so far.
- Sort Of: Salt raises blood pressure simply by increasing blood volume. Equally, low salt is a risk for insulin resistance. Anyone who has ever completed a well formulated LCHF diet is aware of the importance of salt supplementation to prevent low blood pressure and cramps. The same is true for indigenous cultures who eat LCHF diets; they all add about 1.5-2.0 g salt a day.
- No: Where is the convincing evidence to say that saturated fat on its own is a health risk? Here’s a recent meta-analysis of the longitudinal studies in the American Journal of Clinical Nutrition. There is no evidence of an association between saturated fat intake and cardiovascular outcomes in a combined cohort of more than 347,000 adults followed up for between 5 and 25 years.
- No: Eat plenty of breads and cereals, preferably wholegrain, and limit your intake of high-sugar foods. Really? How about going with the more plausible mechanism for how we store fat in fat cells via raised insulin. Insulin, you recall, is raised by carbs, even the so called healthy whole grains. Sugar is an extra baddie – we all agree on that. But the language is so lame, it almost condones anything other than high sugar. Sugar and other insulin raising carbs promote hyperinsulemia, inflammation, glycation, oxidative stress, and fat storage. Because the inevitable outcome of a low fat diet is either starving yourself and keeping insulin under control that way, or a high carbohydrate diet. Either way, this regime is neither sustainable nor healthy in the long run. A low fat diet with sufficient calories for normal living is going to have to also be a high carb diet. Even if you eat lots of extra protein to avoid the extra starchy carbs, you end up with glucose anyway because excess protein will be converted, albeit inefficiently, into glucose in the liver via gluconeogenesis.
- No: A calorie is not a calorie. Calories from different sources have profoundly different metabolic and hormonal effects in the body. Starchy and easily digested carbs raise insulin and insulin chronically blocks leptin. Protein raises insulin but the effect is short lasting and therefore satiating. Fat is metabolically benign in the absence of chronically elevated insulin. This is why an “eat as much as you feel like” LCHF diet out-performs a low fat high carb diet. The way you get weight homeostasis is by controlling insulin. Perversely, the healthy food guidelines most governments push are likely to negatively affect the people who are highest risk the most; i.e. those who are less carbohydrate tolerant and therefore predisposed to excessive weight gain and insulin resistance in the presence of high carb diets.
In the end, it looks a bit like the story about the time I was in a long distance ocean swim. The support kayaker taps me on the shoulder and says “You are going to need a change of strategy”. “Why, I’m swimming flat out already” I reply. “Because you haven’t made forward progress in an hour, in fact I think you are going backwards….”. “I see, let’s talk about our options” I say.
We have to accept that we are making no progress in reducing the epidemic of obesity and chronic disease and we need to consider why. We need a discussion about our strategy. This is the start of that discussion. We all agree that our industrialized food supply is bad but we don’t agree on how to change it and what nutrients are causing the damage. We all mostly agree that sugar is a bad guy, but we can’t all agree that it is the effect of sugar on insulin and insulin resistance that is the problem. Yes sugar has fructose as well which has problems through other pathways. But, whether it’s loads of insulin-raising simple or complex carbs, it doesn’t matter – both need to be given the boot from the healthy food guidelines. In fact, perversely in my view, we ignore the fact that obesity is a metabolic disorder caused by any type of carb. Sure, trans fats and the like don’t help. But let’s name the real VILLAIN here and now. It’s not saturated fat….it’s high carbs.
So what’s the answer?
- Stop doing nutrition research which tests one thing – the low fat dogma against the SAD. This is fundamentally bogus.
- Start doing research which has a start point in biology and evolution by natural selection. That means start with some sort of paleo/primal LCHF as the “probably healthiest option” hypothesis. Humans are omnivores = we eat plants and meat. In human evolution, insulin was hardly ever raised excessively, and if it was, it was probably near the end of summer when man needed to pack away fat to survive the winter.
- Stop pretending we know everything about nutrition. We don’t and we shouldn’t trust anyone who says they do. It’s a science in its infancy with a good deal of poor research behind it and an industry which has infiltrated research and public policy for its own benefit and not ours.
- Start to consider that like many other instances in human history, almost the opposite of what we have preached might be true. Think Galileo, Hormone Replacement Therapy, causes of stomach ulcers, and dozens of times when medicine had it completely wrong. It’s obvious that at least a few of the assumptions behind current healthy eating guidelines are bogus.
If you end up eating too many carbs in the presence of fat, no matter how paleo plant and meat based the rest of your diet, then all bets are off, you will get fat.
I’m writing this expecting to draw the wrath of colleagues, academia, government and medical and research conservatism. Hopefully first though they carefully consider points 1-4 above. What we need to start with is good science. I could be wrong, but so could you.
So let the diet wars commence; we’re in the ring and we’re ready to fight. We’re starting with the hypothesis that carbs make you fat, and that fat keeps you lean. Bring it!
Footnote: There are typically three types of diet commonly and currently discussed; the LCHF diet, a low fat high carb diet and a moderate fat moderate carb diet (SAD). I want to reiterate that the SAD is the deadliest. A well formulated LCHF diet is not high protein, it is only adequate protein. Low carb has nothing to do with dietary percentages. It’s a total carb intake of <100g/day, maybe even <50g/day, or up to 150g/day for athletes. The LCHF approach is often confused by researchers and clinicians because I often see this regime criticised as either high protien, high fat, or the maount of carbohydrate quoted being far too high. Total daily carbs are what are important.
Thanks again to Helen Kilding in writing this blog