Optimal Macro Split for Cutting & Bulking

Embark on a journey to fine-tune your diet for different objectives—be it cutting, bulking, or maintenance.

Through an extensive analysis of dietary data, this article unveils how adjusting your macro split can significantly influence your appetite and body composition. Whether your goal is fat loss, muscle gain, or maintaining your current physique, understanding the right macro split is your stepping stone to success.

Continue reading to uncover how the seasonal rhythm of macro splits can be your game-changer.


What if you could harness the power of your chronobiology to optimise your diet for fat loss (spring), bulking (autumn) or maintenance (winter/summer)?  

Our analysis of half a million days of MyFitnessPal data provides some fascinating insights into how you can dial in your macro ranges to help you optimise your diet to suit your goals.   

If you’re interested in knowing what macro ranges will help you control your appetite to lose fat or to stimulate your appetite to help you bulk up, then read on.  


But first, some context.  (If you don’t want to understand why this works, you can skip straight to the pie charts and tables further down).  To recap the discussion from previous articles:

Macronutrient cycles in nature

While humans today are largely removed from the adaptive pressures of nature, for many animals like Beadnose the bear (pictured here in June 2018 and September 2018) getting fat in preparation for winter is a matter of life and death.  

  • In autumn, these bears eat berries and fatty meat to get big (carbs+fat).  
  • Through winter they hibernate and use up some of their fat (LCHF/keto).
  • In spring and summer, they’re out fishing for lean protein in the thawing river, building back up their muscles ready to start the process all over again (PSMF).  

While hibernating bears are an extreme example of the way nature drives our chronobiology, before the adoption of agriculture, humans would have also experienced cyclical food availability that helped us to build fat for winter in autumn and lean muscle and fat loss in spring.

We are beginning to accept that our biology is intimately linked to our daily circadian rhythm and the effect of light, temperature and food on our bodies.  There are numerous benefits in syncing our light exposure, food and sleep with the daily cycles.   

But what if we are also adapted to an annual rhythm and our biology is synchronised to the annual seasonal rhythms?  Could it be that nature not only provides the ideal food to prepare us for the coming season but that the foods that are available to us in each season also plays a role in regulating our body weight set point and therefore our appetite?  

In modern times, the variation in our environment is less extreme than it would have been in the past.  But nevertheless, some degree of seasonal exists for humans as demonstrated by this data from obese humans from suburban Minnesota.

  • Body weight is at the lowest at the end of summer and increases through autumn up to winter.
  • Fat intake is lowest in spring when carbs are highest.  
  • Carbohydrate intake is highest in summer and lowest in winter.  
  • Activity levels are higher and total calorie intake is lower in summer and lower in winter.  

What foods help us gain fat?

The DIETFITS study showed that we can lose weight on either a low-carb (winter) or low-fat diet (summer). However, in spite of our best efforts, we tend to regress back towards a mixture of fat+carbs whenever they are available to us.

Participants in the DIETFITS study were asked to reduce their carbs or fat as much as possible initially while still prioritising whole minimally processed foods. After this initial period, they were encouraged to increase carbs or fat to the point that they thought was sustainable over the long term.

This drift toward more hyperpalatable energy-dense fat+carb zone is accompanied by an increase in energy intake and a slowing of weight loss (and typically weight regain in the long term).  

This drift towards similar intakes of carb and fat intakes is no longer only happening on an annual basis. Over the past century fat and carbs have drifted towards each other in percentage terms as we have perfected modern agricultural practices, food processing and the widespread use of chemical fertilisers that have enabled us to double our food production.

This growth in both fat and carb availability has corresponded with an abundance of food that has facilitated an increased rate of growth in the number and size of the human population.   

It’s not just America.  We see the same phenomenon in China and the rest of the world.

This chart from Cian Foley of Don’t Eat for Winter shows obesity rates (green line) across various countries (sorted from leanest to more obese, left to right) tend to increase as our diet consists of a similar combination of carbs+fat.   

With this context in place, we can now look at the various macro configurations that can help us minimise our energy intake naturally without exercising massive amounts of willpower that typically fails in the long term.  

Low carb/keto/winter

Moving on to modern times when we can track our food using smartphone apps, the chart below from our satiety analysis of half a million days of food logging from ten thousand people also shows that most of us gravitate to a moderate-fat/moderate-carb intake that tends to lead to maximum calorie intake.

On the left-hand side, we see that there is a lower-carb ‘sweet spot’ between about 20 to 30% carbs when we also tend to eat less. As we push carbs lower this benefit of reducing carbs seems to diminish as we end up with higher fat intakes (i.e. lower carb is not necessarily better for satiety).

As you look at the chart, you may have wondered, “If I want to harness the appetite suppression effects of the low carb diet with 20 to 30% carbs, what should my protein and fat and fibre macros be?”

The chart below shows the average macronutrient split on days where the MFP users obtained between 20 and 30% of their energy from carbs.   The data has also been filtered to show the 50% of days where people reported consuming the least food to identify the ideal macros for weight loss using a low carb approach.

The table below shows the average, 15th and 85th percentiles values the lowest intake days in terms of protein, fat, carbs, sugar, fibre and starch (i.e. this means that 70% of the values lie between the 15th and 85th percentile values).   The last row of the table shows the “typical” macro profile all half a million days MFP dataset for comparison with the low carb macros.

A high-satiety lower-carb diet tends to have significantly more protein, more fat and less starch than average. If you’re following a lower carb diet with the hope of losing weight then you will likely do best if you set your protein is between 21 and 39% of calories with between 35 to 54% of your energy from fat.

Low fat/summer

To the far right of the carbohydrate vs satiety chart below we see that we also get a nice improvement in satiety when we get more than about 55% of our energy from carbs.

The pie chart below shows what this looks like in terms of macros.  Again we have filtered for the days when people reported consuming the least energy on a low-fat diet to identify ideal macro ranges on a reduced-fat diet.

The table below shows the average, 15th and 85th percentile values for the lowest reported intake in terms of protein, fat, carbs, sugar, fibre and starch.  Again, the typical macro splits have been included for comparison with average intakes.

If you want to use a high carb diet (> 55% carbs) to manage your appetite then you will want to target between 11 to 21% protein and 16 to 28% fat.

High protein/spring/PSMF

Nature does an excellent job of leaning us out and building lean muscle mass in spring with higher protein foods with less fat and carbs.  At this rate, it looks like Beadnose will be shredded in time for beach season.

A “Protein Sparing Modified Fast“, which is widely regarded as the most effective way to lose weight, provides adequate protein to preserve lean mass with minimal energy dietary from fat or carbs.

In this scenario, we’ll use a cut off of greater than 35% protein based on the plot of protein vs satiety below.  We want to understand if you push your protein above 35% do your carb and fat macros matter?

The pie chart below shows what the spring style diet looks like in terms of macros.  Again, we’re looking at the macros on days when people reported eating the least.

The table below shows the average, 15th and 85th percentiles values for the lowest energy intake days in terms of protein, fat, carbs, sugar, fibre and starch.  

The range of fat and carbs is quite wide.  It seems that fat and carb intake doesn’t seem to matter much.   Fat can be anywhere between 21 and 46% with carbs anywhere between 14 and 39% of calories.  

The weighting towards more fat than carbs makes sense because protein and fat usually come together in the same package.  You wouldn’t intentionally be adding any extra fat in this scenario, but rather prioritising leaner options.

There is no definitive definition of a protein-sparing modified fast, but as you can see from the protein vs satiety chart above not many people are able to maintain a diet with more than 40% of their energy from protein. Protein is very satiating and it is hard to convert protein to energy once you have satisfied your body’s need for protein.

However, if you are serious about fat loss then manipulating your diet to minimise the amount of energy from fat and carbs seems to be a good strategy.

Fat+carbs (autumn)

While spring seems to lean us out and build muscle after winter, like Beadnose the bear, autumn seems to be the time that we pack on the fat.  

Image result for fat bear week

If you are looking to bulk up and gain weight, then you may want to harness the power of autumnal-style foods to help increase your appetite, ghrelin and insulin levels.  

The satiety chart below shows us that we tend to increase our energy intake once the amount of energy from fat+carbs starts to increase above about 65% (or when protein and fibre start to decrease).

The combination of fat+starch (shown below) seems to be even more effective at stimulating us to eat more (but most people don’t think in terms of the percentage starch content of their diet).  If you want to put on fat fast, then anything that lists some combination of refined starch (corn, rice, wheat) with refined oils will do the trick nicely!!! Conversely, if you want to avoid fat gain, then you should do whatever you can to avoid these foods!

The chart below shows average macros when the combination of fat+carbs is greater than 65% of energy intake based on the MFP data analysis.  In this scenario, we have focused on the highest energy intake to identify the macronutrient splits that would maximise appetite and energy consumption.  

The table below shows the average, 15th and 85th percentiles for terms of protein, fat, carbs, sugar, fibre and starch.   Compared to the typical intake, these autumnal foods have significantly less protein and a little more fat and starch.

So, if your goal is to gain fat in a hurry, then targeting lower protein less than (9 to 13%) with moderate fat (27 to 48%) and moderate carbs (41 to 62%) will be helpful.

However, if like many people these days, you are trying to cut back on calories, lose some fat and reverse your diabetes you should do everything in your power to avoid meals with this macronutrient profile!

If you are just looking to gain muscle without too much fat then it’s a better strategy to maintain your protein intake while dialling up your energy from fat and carbs to support growth and recovery

Comparison of approaches

The chart below compares the macros for the different approaches side by side.   Sugar and fibre remain relatively constant, while it’s protein and starch that tend to change the most between the different ‘seasons’.  

The chart below shows the % of the goal calories logged by each of the groups compared to the average.  If the number is less than 100%, it means that the MFP users logged less than their goal while if the number was higher than 100%, it means the users logged more than their calorie goal.

The summer (higher carb) and winter (lower carb) diets both provide similar levels of satiety, while the spring (high protein) is slightly better if your goal was appetite control or weight loss. As noted above, you can leverage the appetite suppressing effect of the spring/PSMF approach further by reducing the energy from fat and/or carbs.

Interestingly, this relationship between energy intake and macronutrient combinations aligns with this study using adlib feeding in rats which concluded that “the signal for overfeeding originals in the liver when both fatty acids and glucose are available for oxidation.”

It seems there is something more than just energy density or palatability going on here. It’s the hyper autumnal filling of both our fat and glucose storage at the same time with low protein that really drives us into a feeding frenzy. Our brain is programmed to find these foods incredibly hyper-palatable because they are so effective at enabling us to store fat when they are available to help us prepare for winter!

How we’ve used this understanding to fine tune the Nutrient Optimiser algorithm

This understanding of optimal macro ranges for different goals is central to our design of the Nutrient Optimiser to help you identify the foods that will help you reach your goals.

  • We don’t set fixed macro percentages because there is a wide range of approaches that work. Focusing on fixed macro targets mean you don’t have as much flexibility to focus on nutrient density.
  • If you’re looking to bulk up we use the satiety formula to design a lower protein moderate fat, moderate carb diet.
  • If your preference is low carb or you are managing blood sugars and trying to lose weight we target a lowered carb approach, with carbs reduced enough to stabilise blood sugars but not so low as to compromise satiety.
  • If your preference is high carb low fat we can help you design the most nutrient dense diet.
  • And if you want to target maximum fat loss we prioritise protein with less energy from fat and carbs (i.e. spring/PSMF).

Take away

The chart below shows the macro splits for all four seasons.  While each season is different.

  • If your goal is to bulk up, the lower protein autumnal approach will do the trick nicely.  
  • If you are trying to restrict your calorie intake without paying attention to satiety or food quality, your chances of long-term success are low.  
  • If you are managing diabetes and trying to stabilise your blood sugars and lose weight, then a lower carb diet will likely be the most helpful.  
  • However, if you are metabolically flexible, then you might be able to jump around from day to day or even meal to meal between these macros, so long as long as you stay out of the hyperpalatable danger zone.  
  • Don’t forget that nutrient density is a critical consideration to ensure you are getting the micronutrients you need from your diet.  
  • Regardless of macronutrient profile, nutrient density always aligns with satiety.  

I hope the insights gained from the seasons combined with the MFP data analysis will help you achieve your goals.  Even if you don’t buy into the chronobiology angle, it can be a useful way to frame your food choices and the macro profile are a good guideline to help you identify which foods and meals to prioritise and avoid.  

How Can I Calculate My Nutrient Intake?

If you’re interested in checking if you’re getting just enough dietary phosphorus, you can check your nutrient profile using our Free 7-Day Nutrient Clarity Challenge

After a week of tracking your current diet in CronometerNutrient Optimiser will give you a prioritised list of foods and NutriBooster recipes that will help you plug your current nutritional gaps.

Level Up Your Nutrient Density

To help you level up your nutrient density, we’ve prepared a Nutritional Optimisation Starter Pack to ensure you are getting plenty of all the essential nutrients from the food you eat every day.    

The free starter pack includes:

  • Maximum Nutrient Density Food List
  • Sample Maximum Nutrient Density Recipe Book
  • Sample Maximum Nutrient Density Meal Plan.

To get started today, all you have to do is join our new Optimising Nutrition Group here

Once you join, you will find the Nutritional Optimisation starter pack in the discovery section here.

Further reading

2 thoughts on “Optimal Macro Split for Cutting & Bulking”

    • “I acknowledge that hibernating bears are an extreme example of the way nature drives our chronobiology. But, before the adoption of agriculture, humans would have also experienced cyclical food availability that helped us to build fat for winter in autumn and lean muscle and fat loss in spring…”

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