Keto Lie #3: You should eat more fat to burn more body fat.
One of the most common responses to any weight loss stall in many keto groups is that you should ‘eat more fat to get your ketones higher and burn more fat’.
This lie is seductive because it is partly correct, as well as delicious! High-fat foods are highly palatable and provide a dopamine hit that makes us feel great and gives us a quick energy rush.
But it’s important to understand whether your goal is to burn the fat in your diet or the fat on your body. This distinction is important if you are going to achieve your goals in the long term.
Like all the macronutrients, dietary fat tends to be a controversial and divisive topic. And as with many popular myths, there is an element of truth to the belief that eating fat will enable us to burn fat.
It’s understandable that many people have swung hard to the other extreme. We’ve been told for the past half-century (since the 1977 Dietary Guidelines) that we should avoid fat, particularly saturated fat and cholesterol. However, despite obediently reducing these ‘bad foods’, the obesity epidemic has marched on, seemingly unabated.
The charts (with data from the United States Department of Agriculture Economic Research Service and the Centres for Disease Control) show that, in line with the guidance, we have obediently reduced the percentage of energy in our diet from both saturated fat and cholesterol. This has been achieved by eating fewer animal products and more high-profit margin refined grains, sugars and seed oils from large-scale agriculture.
So, when we were told that we could eat fat and get skinny, plenty of people jumped on board, swinging to the other extreme, believing that fat could do no wrong. However, a recurring theme of Optimising Nutrition is that the optimal is rarely found at the extremes, including when it comes to the food we eat.
We love thinking in terms of ’ON vs OFF’, ‘black vs white’, ‘right vs wrong’, and ‘us vs them’. But it’s rarely that simple!
So, does replacing carbs with fat help you to eat less and lose weight? Let’s see what the data tells us.
Stanford University (in partnership with Gary Taubes and Peter Attia’s Nutritional Science Initiative) carried out a ground-breaking, year-long major study with more than 609 participants (Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial). They found that (regardless of genetics, insulin levels or blood sugars), participants following either the low-fat or low-carb diet all achieved similar weight loss and improvements in metabolic health.
The researchers initially encouraged participants to pursue a diet as low in carbs or fat as they could achieve. They then asked them to back off to a level that they thought was sustainable.
The key observations from the Stanford DIETFITS study were as follows.
- Following either a low-carb or low-fat diet can help to reduce the hyperpalatable, highly processed junk food in our diets that typically causes us to eat more than we need to.
- Over time, most people gravitate back to hyperpalatable junk food (which is typically a combination of nutrient-poor fats and carbs together).
- It was the people that changed their DIET QUALITY who had the most significant long-term success. These people experienced increased satiety and no longer felt like slaves to their appetite.
Lead researcher Professor Chris Gardner stated that, rather than pursuing a magic macronutrient ratio, defining diet quality in a way that leads to satiety is the next exciting frontier of nutritional science. Empowering people living in the real world to gain control of their appetite will free them from having to weigh and measure everything they eat and without continually having to fight their hunger.
In a similar vein to the DIETFITS study, Kevin Hall’s group at the NIH recently published, A plant-based, low-fat diet decreases ad libitum energy intake compared to an animal-based, ketogenic diet: An inpatient randomised controlled trial. Their goal was to compare the macronutrient extremes, with a 75% carbohydrate (PBLF = plant-based low-fat) vs a 75% fat ‘well-formulated ketogenic diet’ (ABLC = animal-based low carb).
There is no argument that the people on the keto diet were in ketosis. Blood ketone levels reached 2.0 mmol/L towards the end of the 2 weeks during the low-carb diet (ABLC = red line). Interestingly, people on the low-fat plant-based diet (PBLF = green line) also had elevated ketones as they started to burn fat for the first few days.
Blood glucose levels were more stable and a little lower on the low-carb diet (ABLC = red bars). HbA1c, average glucose and insulin levels improved on both diets, but slightly more on the low carb (ABLC = red bars).
There was a flatter and smaller blood sugar response on the low-carb diet (ABLC = red line) compared to the low-fat diet (PBLF = green line).
However, as per the study headline, on average, participants ate significantly fewer calories on the low-fat diet (PBLF = green line)!
Participants on the low-carb diet lost more weight than on the high-carb diet (although the difference between the two groups was not great enough to be statistically significant).
Weight loss on the keto approach was more water weight (due to a reduction in the water held with glycogen in the liver), whereas those on the low-fat diet lost slightly more body fat. Note: every gram of glycogen is stored with 4 grams of water; hence the more significant initial weight loss as blood sugar dropped.
While the Twitterverse lit up with both plant-based and keto camps claiming that their team won, the reality is the results were pretty much even. Similar to the DIETFITS study, everyone lost weight when they moved away from the hyperpalatable processed foods that are typically a combination of fat and carbs together.
So, if it’s not about carbs or fat, why do we still have an obesity epidemic? It seems we need to go beyond thinking in terms of carbs vs fat.
Unfortunately, neither study tested a control arm in the middle. I would have loved to see what would have happened if they compared it with a diet between the two extremes that contained a similar blend of carbs and fat together.
Fortunately, our satiety analysis helps to fill in these gaps. The chart below is from our analysis of 587,187 days of food logging. The vertical axis shows their actual calorie intake in MyFitnessPal divided by their target calorie intake. A value toward the bottom means that they consumed less than their goal (and vice versa). We divided the days of data up based on their carbohydrate intake (shown on the horizontal axis).
As indicated by the green line, we tend to eat a greater quantity of food when that food contains a combination of fat and carbs (e.g. doughnuts and croissants). As we move toward the left, reducing the carbohydrates in your diet does indeed tend to help us eat less, but only up to a point. The best satiety outcome tends to occur when carbohydrates make up about 25% of total calories. To the right, we see that it is tough to over-consume foods that have a very high carbohydrate content and very low-fat (e.g. broccoli, plain rice and plain potato).
Dopamine is a neurotransmitter that makes us feel good, that reinforces behaviours that are generally beneficial and helps us form habits that ensure our survival. Some examples of things that produce dopamine include eating food that contains energy and/or tastes great because it has the nutrients we need, learning something new, sex, etc.).
The combination of fat plus carbs provides the biggest dopamine hit because it enables us to fill both our fat and glucose storage tanks at the same time. This observation aligns with a 2018 study in Cell Metabolism, which showed that fat+carb foods give us a ‘supra-additive’ dopamine reward.
This relationship between energy intake and macronutrient combination also aligns with Body fat and the metabolic control of food intake (Friedman 1990) using ad libitum feeding (i.e. as much as they wanted) in rats, which concluded that ‘the signal for overfeeding originates in the liver when both fatty acids and glucose are available for oxidation’.
Our brain is programmed to seek out these fat+carb combo foods and find them incredibly delicious because they are so effective at enabling us to obtain calories quickly and store fat! These energy-dense foods are rare in nature (other than in autumn to help animals prepare for winter). However, today the fat+carb formula is the basis of the vast majority of processed foods.
Food manufacturers and most recipe book creators have perfected the art of combining refined grains and sugars with processed vegetable oils that make food palatable, so you eat more. These foods also typically contain added flavourings and colourings to trick our brains into thinking they contain the nutrients we require (but they don’t).
‘The food problem is a flavour problem. For half a century, we’ve been making the stuff people should eat–fruits, vegetables, whole grains, unprocessed meats–incrementally less delicious. Meanwhile, we’ve been making the food people shouldn’t eat–chips, fast food, soft drinks, crackers–taste ever more exciting. The result is exactly what you’d expect.’
― Mark Schatzker, The Dorito Effect: The Surprising New Truth About Food and Flavour
Many people report a spontaneous reduction in appetite when they reduce the processed carbs in their diet. However, it appears that the main benefit of a low-carb, high-fat diet comes from reducing carbohydrates, which moves us away from hyperpalatable fat+carb foods (i.e. it’s NOT the focus on eating more fat).
The frequency distribution (blue bars) shown in the carbohydrate vs satiety chart below demonstrates that most people gravitate to these low satiety foods that contain around 40% of their energy from carbs with a similar amount of energy from fat.
To the right of the chart, we see that not many people manage to eat very high-carb, low-fat diets that can lead to much lower energy intake. There are groups of people who follow a whole food plant-based diet (with minimal fat) that demonstrate that this is the case (although the profile of bioavailable micronutrients may be less than optimal).
While it’s hard to get fat on a diet consisting only of fruit and vegetables with no added oil, it also requires a significant amount of time to prepare, so most people end up adding refined oils to ensure they get the energy they crave.
When we move to the left, we see that a lower-carb diet (i.e. 20-30% carbs) provides an improved satiety response and a lower ad libitum calorie intake. However, moving to an even lower carb intake is not necessarily better.
Many people find that reducing processed carbs and not fearing fat in the early days of a low-carb or keto diet is helpful. Their blood sugars stabilise, and they lose a lot of water weight. As noted earlier, for every gram of glycogen in the liver and muscles you store 4 grams of water, so as you deplete glucose you also lose a significant amount of water, i.e. weight on the scale. If you slash all your carbs and don’t replace it with fat, you’ll likely feel overly hungry, and you won’t stick with it, so it can be smart to just reduce carbs without focusing on cutting fat initially.
Low-carb foods also tend to contain more bioavailable proteins, which boost satiety so that people feel fuller, and they can then control their weight without tracking their food. They fall in love with their effortless new weight loss and believe all the benefits are due to the fat they are eating (not the reduced carbs or the higher protein). However, a low-carb, high-fat diet often works for a while… until it doesn’t.
Once you’ve gained the satiety benefits of more bioavailable protein and moved away from the hyperpalatable carb+fat danger zone, sometimes the hardest, but most necessary step, is to start to dial back the dietary fat as well.
Like stealing a new toy from a baby, it can be hard to reduce the dietary fat if we’ve been told, and believed, that we could have as much of it as we wanted. But it may be necessary if we’re going to continue to make progress in terms of fat loss and diabetes reversal.
For continued weight loss, we need to think in terms of eating to get the nutrients we require (i.e. protein, vitamins and minerals) from the food we eat, while allowing the excess energy stored in in our body to be used (i.e. both stored glucose in your liver and blood and fat in your adipose tissue).
Reducing carbs and eating ‘fat to satiety’ is a simple way for many people to initially move away from the fat+carb danger zone. But once your progress stalls, it’s time to look to reduce dietary fat as well if you want to increase satiety further, manage your appetite, and continue to burn the fat on your body. ‘Eat fat to burn fat’ is poor advice that rarely leads to more optimal body composition in the long term.
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Nutrient density is where it’s at, and I agree entirely that each person needs to figure out their own carbohydrate tolerance.Professor Mark Cucuzzella MD FAAFP
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WVU Centre for Diabetes and Metabolic Health
There are many myths and misconceptions on low carb and ketogenic diets. Learning how to do the diet correctly from the beginning will make a big difference, especially on your medium to long term results and health.
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Big Fat Keto Lies is a must-read for anyone who has stalled on their path to health and optimal weight. Data-driven engineer Marty Kendall unpacks the common keto dietary conventions that typically cause people to fail in the long-term.
Marty, through easy to follow discussions, explains the often neglected but importance of focusing on dense foods to control appetite – beyond simply looking at macros and calories.
If optimizing your health and nutrition is your goal, you will not be disappointed.
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Denver Colorado, USA
Every popular diet contains some truth and, as time goes on, ever greater outlandish, hyperbolic and inaccurate claims.
Marty Kendall does a superb job at dispelling the many myths of the keto diet that have grown up over the past few years but offers us a legitimate solution based on his analysis of many large data sets.
Big Fat Keto Lies is an essential read for anyone wanting to step out of all pop culture diet trends and embrace a truly agnostic form of nutrition for health.Aimee Gallo
Master’s in Nutrition and Functional Medicine
If your goal is to healthfully lose body fat using the most up to date nutrition science and don’t know where to start, I highly recommend Big Fat Keto Lies, by Marty Kendall.
As a Harvard-trained radiation oncologist, integrative oncologist and functional medicine practitioner, I have spent nearly two decades counselling patients on the importance of reducing body fat and insulin resistance. During this time, I have witnessed countless patients try unsuccessfully to lose weight or maintain their weight loss using the latest “fad diets” (including the popular ketogenic diet and intermittent fasting). Once you read Big Fat Keto Lies, you will understand why these approaches often don’t work.
Marty explains, in a very approachable manner, the reasons why people are biologically programmed to fail on most weight-loss diets or calorie restriction. In Big Fat Keto Lies, you will also learn practical, effective, healthful and sustainable approaches to fat loss that are simple to understand and implement. I will be recommending this book for all of my patients who want to optimize their metabolic health, lose body fat and improve their anticancer biological terrain.Dr Brian Lawenda, MD
Medical Director, Northwest Cancer Clinic;
National Director of Integrative Oncology and Cancer Survivorship,
GenesisCare, Kennewick, WA
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