The Nutrient Showdown: Why Low-Carb and Low-Fat Diets Both Work

Have you ever wondered why there’s a never-ending debate between the low-carb vs low-fat and carnivore vs plant-based camps? 

Despite decades of research, spending hundreds of millions of dollars and seemingly infinite bickering online, the forever war continues with no sign of a cease-fire.

Both are equally enthusiastic about the approach that worked for them and their fellow tribemates.  

But there seems to be no common ground with the enemy!

It’s as if they’re talking a different language. 

Are they seeing a completely different version of reality!?!?

To help us understand the alternate worlds, by looking at the low-carb and low-fat data, in this article, we’ll dive into the satiety response to:

  • protein
  • carbs and
  • fat. 

Highlights

  • Reducing either carbs or fat aligns with eating less.  This is because it moves us away from the carb+fat danger zone. 
  • Satiety is multifactorial.  However, energy density is the dominant satiety factor for people with a high-carb diet.  Meanwhile, protein is the dominant satiety factor on a lower-carb diet. 
  • If your protein % is higher, energy from both carbs and fat will be lower, so it doesn’t matter if you’re getting a little bit more energy from fat or carbs.   

Satiety Response to Carbohydrates

To create the charts, I segmented the data:

  • Low carb – less than 43% carbohydrate (i.e. the bottom third of the carb intake) and
  • Low fat – less than 25% fat (i.e. the bottom third of the fat intake).

Low carb diet

Our first chart shows the satiety response to carbs on a low-carb and low-fat diet together.   

For the person getting most of their fuel from fat, reducing carbs from 43 to 20% feels almost magical!  This reduction in carbs also usually coincides with a significant increase in protein, which is likely doing most of the heavy lifting in the satiety department, not the carbs. 

Low Fat Diet

However, the person on the low-fat diet experiences something completely different.  They’ll eat less if they push their fat and protein REALLY low and wind carbs up past 75%. 

Many traditional cultures (e.g. Okinawans, Kitavans and Tarahumara people) live on high-carb diets consisting of sweet potatoes, yams, rice, maize and taro. 

If your fat is low, there’s a carb bliss point (or the Goldilocks zone where you’ll eat the most), at around 63% carbs with 25% fat and 12% protein.   

This snip from our food search tool below shows the foods — like fruitcake, hot cross buns, scones, brioche bread and French fries — that fit into this magical window.   

But if our fat is low and we dial carbs below 60%, protein leverage kicks in, and we eat less.  At the bottom of the chart, someone with 30% carb and 25% fat would consume 45% protein.  But once we dial up protein, there’s not much difference between high satiety low carb and high satiety low fat.   

Satiety Response to Fat

Next, let’s look at fat. 

Low Fat Diet

Someone on a low-fat diet (less than 25% fat) could dial back their fat even further, but there’s not much room to move.   When we reduce fat to below 20%, obtaining enough essential fatty acids becomes harder, so you’re probably better off dialling back carbs.

Low Carb Diet

But what about if your carbs are already low?  Should you increase or decrease your fat to increase #satiety and lose weight? 

If you ask online, you’ll probably get a response along the lines of “You’ve just got to get MORE fat in to increase your #ketones and lower your #insulin, and you’ll break that stall.”  

But the data shows the opposite! 

If your carbs are low, dialling back your fat aligns with eating less.  Satiety starts to really kick in on a low-carb diet when your fat drops below 40% fat with plenty of protein.   

Satiety Response to Protein

Protein leverage seems to be a bigger deal in the low-carb space, while the low-fat and plant-based crowd seem ambivalent about protein. 

When we see the satiety response to protein on a low-carb vs low-fat diet, we can appreciate why this is the case. 

Satiety Response to Protein – Low Fat

The relationship between protein and energy intake is a gentle slope for people on a low-fat diet, who typically get less protein than the low-carb crowd (i.e. average protein on low fat = 14% vs average protein on low carb = 27%).

Satiety Response to Protein – Low-Carb

However, if your carbs are low, protein leverage kicks HARD. 

Moving from 15 to 50% protein aligns with a 45% reduction in energy!   

That’s why, in our Macros Masterclass, we guide people to incrementally dial up their protein % to achieve sustainable fat loss.  If you go from zero to hero overnight, you will be hungry due to the massive energy deficit, which is not sustainable (you were warned).

The powerful protein leverage response makes modelling satiety pretty easy for the lower carb end of the spectrum.  However, to accurately model satiety for a low-fat diet, we have to consider energy density minerals and even vitamins (but that’s a topic for another article). 

Energy Density

While not a macronutrient, energy density is worth mentioning.  Images like this are pretty popular in low-fat circles. 

Professor Barbara Rolls, author of the Volumetrics diet, encourages people to consume watery soups, fruits and veggies to fill their stomachs.  While this may provide short-term satiation, it may not be great for long-term satiety if you’re hungry again in a couple of hours.   

Unfortunately, most RCTs that have quantified satiety only measure how hungry you are a couple of hours later.  In contrast, our data shows how much people eat over the whole day, thus allowing us to identify the parameters and eating patterns that align with long-term satiety.   

Our final chart shows the similarities but differences in energy density for low carb vs low fat.  

  • For both scenarios, there’s an energy-density bliss point that aligns the magical combination of carbs+fat with lower protein.
  • Whether more of your energy comes from carbs or fat, a higher protein % aligns with eating a lot less. 
  • But very high-fat foods aren’t as satiating as the steak. 
  • Meanwhile, you won’t get fat if you live on only fruit or non-starchy vegetables. 

Once we understand the inverted U-shaped satiety response to energy density, predicting satiety for a lower-fat diet is pretty helpful.  But it’s not helpful for the lower-carb scenario where protein leverage dominates. 

Which One is Better?  Low Carb or Low Fat? 

Before the days of agriculture, food storage and processing, we didn’t have the luxury of choosing whether we preferred a low-carb or low-fat diet.  We ate whatever was available based on the season and location. 

Carbs would have been more plentiful in summer and closer to the equator, while fat and protein would have been the dominant fuel source towards the poles and in winter.  Autumn was a magical time when carbs and fat were available simultaneously, enabling us to eat more and fatten up to survive the impending winter.  But today, our modern food system provides us with a continual feast of autumnal fat+carb foods. 

To escape autumn, we can move towards winter (low carb) or summer (low fat). Both will provide greater satiety per calorie than the constant barrage of autumnal food engineered to hit our bliss points. 

I prefer a lower-carb approach, which usually provides a higher nutrient density than modern processed carbs.  It also provides better glucose stability for many people who are insulin-resistant, which can improve appetite control.  But with some effort, you can create a healthy diet to maintain weight in either scenario.

But the reality is that for weight loss, when we increase the concentration of protein and nutrients, we end up in spring, regardless of which direction we come from. Once you increase the protein percentage, carbs and fat reduce, making it a null argument. 

Summary

  • I hope this article has helped to flesh out how the satiety response to carbs, fat, protein, and energy density differs between a low-carb and a low-fat diet.   
  • Satiety is complex, multifaceted and fascinating. 
  • However, a deeper understanding of the multiple factors can help you optimise for less hunger and avoid overeating, regardless of your dietary preferences. 

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2 thoughts on “The Nutrient Showdown: Why Low-Carb and Low-Fat Diets Both Work”

  1. It would be interesting to see what a “diet” that follows the circannual cycle looks like in regard to what foods during the seasons and recipes

    Great information, thank you!

    Reply
    • I’ve got a few more articles in the pipeline on this fascinating topic.

      Eat foods that are fresh and sourced locally is a good starting place.

      Reply

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