Episode 8 – Flexible Dieting

Key Topics Covered


  • If It Fits Your Macros (IIFYM) as a concept involves the idea that if you hit your macronutrient targets, regardless of how you get there, the body composition outcomes will be the same.
  • Flexible dieting is similar and often an interchangeable term. We are not sticklers for definitions, but personally would use “flexible dieting” as a broader term that is a little bit more like the 80/20 rule (80% of calories coming from whole, nutritious foods, 20% coming from whatever you want). It also can be more flexible in a broader sense of not having to strictly hit macro targets every single day, or other additional ways of adding flexibility into the process.

IIFYM Origin

  • IIFYM originally started on bodybuilding forums to answer questions like “does it matter if I switch my steak to chicken” in regards to the impact on muscle gain or fat loss. Instead of typing long-winded answers, people would say “IIFYM.”
  • The initial concept still involved making sure the majoirty of your diet is based on nutrient-rich foods and getting a sufficient amount of fibre.
  • Over time it developed into a concept that may have been taken a bit too literally by some people, where macros became the ONLY thing that matter. People would start trying to fit as much junk food into their macros as they could – but this was never the original intention of the concept.

Micronutrient Discussion

  • ~80% of your maintenance calories is required to reach micronutrient targets, on average, based on the USA numbers.
  • Obviously you could be an outlier and have a tonne of super nutrient rich foods like organ meats and low-calorie foods that contain micronutrients like vegetables, which would warp this stat. But on average it takes ~80%.
  • This is worth being aware of if 1) <80% of your calorie intake is coming from nutrient rich foods 2) You are in a calorie deficit that involves consuming <80% of your maintenance calories.


  • 40g of sugar has a similar impact on body composition as 40g of carbs from other sources – as mentioned in episode 6.
  • Sugar is easier to overconsume though. Typically people incidentally end up consuming more calories and less micronutrients if they have more added sugar in their diet.
surwit et all 1997 sugar and body composition

Fat Intake

  • The type of fat doesn’t effect body composition much. Obviously, there are other health benefits etc, but it doesn’t impact body composition much. 
  • There are random studies here and there showing some benefits for body composition for certain types of fat. 
  • 2014 study (Rosqvist et al) comparing large amounts of palm oil to sunflower oil in a matched 750kcal surplus showed that while the weight gain was equal, the sunflower oil group gained 3x as much lean mass, and therefore far less fat as well. But the total change in body mass over the duration was ~1.5kg over 7 weeks. It is hard to make strong claims based on that.
Rosqvist et al 2014 study infographic jorn trommelon


  • Total daily intake matters most.
  • Protein priorities discussed are explained in the images below.
protein prioritisation pyramid
optimising protein intake for athletes

Flexible Dieting Benefits

  • Reduced feelings of restriction.
  • Can make the process easier. It allows you to still make progress in different contexts too e.g. if travelling or with different food circumstances. Some other dietary approaches might not allow for this.
  • It is relatively easy to adjust. For example if you are not losing weight on keto, what is the next step? If you do not have calorie awareness, it is harder to make adjustments. Flexible dieting allows you to mathematically make adjustments based on data.

Flexible Dieting Downsides

  • Risk of disordered eating – not relevant for everybody and there are steps that can be taken to mitigate it. But statistically speaking, the risk is high.
MyFitnessPal and Male Eating Disorders Statistics
  • The disordered eating stats are likely more concerning in women.
  • There is less of an emphasis on micronutrients and fibre.
  • Sometimes people make weird or poor nutritional decisions at the end of the day if they have a specific amount of certain macros leftover.
  • Tracking calories take time/planning. Some other dietary approaches could be simpler and quicker.
  • Processed foods lead to less calorie expenditure from diet induced thermogenesis in comparison to unprocessed foods.
Less calories burned from processed food
  • It is harder to overconsume calories if sticking more to unprocessed foods. The added flexibility sometimes makes it more difficult to avoid overconsuming calories.

Studies Mentioned

  • Surwit et al 1997 – high sugar vs low sugar had the same outcomes for fat loss when calories and macros were matched.
  • Rosqvist et al 2014 – palm oil vs sunflower oil in a 750kcal surplus had noticably different body compositon outcomes.
  • Linardon et al 2019 – My fitness pal usage in men: Associations with eating disorder symptoms and psychosocial impairment.
  • Barr and Wright 2010 – Postprandial energy expenditure in whole-food and processed-food meals: implications for daily energy expenditure.
  • Hall et all 2019 – Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake.

Useful Blog Post