Instead-of-What Substitution Test
Judge a dietary change by what it replaces, not by the removed food alone
- Difficulty
- Easy
- Time to result
- ~days to results
- Steps
- 4
- Confidence
- 92%
Berry repeatedly asks an essential comparison question: instead of what? Removing a food or nutrient does not create an empty space; another source of energy or another food usually replaces it. The replacement can determine the result. In the episode, she says analyses of saturated-fat substitution can support apparently opposing headlines when one comparison uses refined carbohydrate and another uses whole grains or unsaturated fats. The practical test is to name both sides of the swap, identify the outcome and time period, and look for evidence on that exact comparison. This turns an absolute claim such as “saturated fat is fine” or “saturated fat is harmful” into a more precise decision about one replacement. It is an evidence-interpretation rule, not a prescription for any individual diet.
Origin
Extracted from The Diary of a CEO
Core principles
- 01Every removal creates a replacement
- 02The comparator can reverse the apparent conclusion
- 03Compare like-for-like outcomes and time periods
- 04Prefer conclusions supported across multiple controlled comparisons
How to run it
- 1
Define the removal
Specify the food, nutrient, or pattern being reduced and the amount or context involved. Avoid broad labels that combine materially different foods.
Pro tip Use the same level of specificity on both sides of the comparison.
Watch out A category such as dairy can conceal very different food structures.
- 2
Name the replacement
State what will fill the dietary role of the removed item. Distinguish whole grains from refined carbohydrates and unsaturated fats from trans fats.
Pro tip If a source does not disclose the comparator, treat its conclusion as incomplete.
Watch out Comparing a food with an unusually poor substitute can make it look better than it is.
- 3
Match the evidence
Look for trials or analyses that study the exact substitution and relevant outcome. Keep short-term markers separate from disease events or mortality.
Pro tip Check whether the food formulation used historically still matches products used today.
Watch out Mechanistic theory or correlation alone may not show the effect of the real-world swap.
- 4
Write the conditional conclusion
Express the result as a comparison: replacing A with B was associated with or produced C in the cited evidence. Preserve uncertainty and study limitations.
Pro tip Use the narrowest conclusion the evidence supports.
Watch out Do not convert population evidence into individualized medical advice.
In the wild
Berry describes a large body of trials in which saturated fat was replaced with different alternatives. She says replacing it with whole-grain carbohydrate or mono- or polyunsaturated fat improved measured health outcomes, while replacing it with refined carbohydrate did not produce the same advantage.
→ The comparator explained why the same analysis could generate conflicting headlines.
Berry argues that a 1970s seed-oil study is often misapplied because the intervention used partially hydrogenated products containing trans fats. Her interpretation is that the historical formulation, rather than modern seed oil as a category, changes what the study can support.
→ Checking the actual replacement and formulation narrowed the claim that could reasonably be made.
Common mistakes
Leaving the comparator unnamed
A removal-only claim hides the alternative that may be driving the outcome.
Combining unlike replacements
Refined carbohydrate, whole grains, trans fats, and unsaturated fats should not be treated as interchangeable comparators.
Turning a comparison into an absolute
Evidence that A performed better than B does not prove A is universally beneficial.
Is it for you?
Best for
People interpreting nutrition studies or choosing between realistic food substitutions.
Not ideal for
It cannot determine personal medical suitability without clinical context and relevant evidence.
From the transcript
“we have to always think of that instead of what”
“if you replace saturated fats with whole grain carbohydrates you have an improvement in health”
“they're talking about the same study”
From the episode
Leading Nutritional Scientist: Seed Oils Are Not Bad For You! Eating This Twice A Day Will Help Menopause! The Alarming Link Between Chewing & Belly Fat!