Study analysis · Nature Metabolism · 2025
You can eat junk food and still lose weight—here's how.
Even if it's all junk food, eating more protein and fewer carbs makes you eat less and burn more calories.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study is like a fair test where 21 people ate two different kinds of ultra-processed meals for a few days, and scientists measured exactly how much they ate and how many calories they burned. It shows that one kind of meal made them eat less and burn more — so we can say this diet caused those changes in the short term.
What’s the bottom line?
Even if the food is ultra-processed (like packaged snacks), eating more protein and less carbs makes your body burn more calories and feel fuller faster.
How strong is this study?
This study was very well done because everyone ate the same meals in a special room that measured every calorie, and they didn’t know which meal was which. But it only lasted a few days and only included young, healthy people — so we can’t say it works for everyone or for a long time.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
70 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=21)+2.0/20
- Follow-up+10/10
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 577 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Limited to short-term effects in healthy young adults; cannot generalize to long-term outcomes, older populations, or those with metabolic disease.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding disclosures were reported in the study text.
The study lacks any declared funding source, conflict of interest statement, or author affiliations with industry. While the absence of disclosure raises a general transparency concern, there is no evidence of actual conflict or industry influence in the reported methods or results.
Key takeaways
- 01
People ate 196 fewer calories per day, burned 128 more calories per day, and had a 14% better energy balance (less fat gain) on a high-protein ultra-processed diet.
- 02
Yes — cutting 196 kcal/day is like skipping a small snack daily, which could lead to weight loss over time.
Surprising findings
- Gastric emptying was faster on the high-protein diet, yet people ate less.Common belief is that slower digestion = more fullness. But here, faster gastric emptying with high protein still led to reduced intake—challenging the idea that protein works by delaying stomach emptying.
- Despite eating 196 fewer calories, participants still had a positive energy balance (+18%).Even with improved energy balance, overeating persisted—meaning high protein doesn’t fully prevent weight gain from ultra-processed foods, just reduces it.
- Fat oxidation increased while carbohydrate oxidation decreased—even though participants were in positive energy balance.You’d expect excess calories to be stored as fat. But the body shifted to burning more fat and less carbs, suggesting protein changes how energy is partitioned—not just how much is consumed.
Practical takeaways
Swap one daily ultra-processed snack (e.g., chips or granola bar) for a high-protein version (e.g., protein bar, high-protein yogurt) to reduce daily calorie intake by ~200 kcal.
This only worked in healthy young adults; results may not apply to older, obese, or insulin-resistant populations. Long-term effects are unknown.
medium confidenceAim for 30% of daily calories from protein—even if your meals are processed—to naturally reduce hunger and increase calorie burn.
Excess protein intake may strain kidneys in susceptible individuals and could increase insulin/glucagon resistance over time.
medium confidenceChoose ultra-processed foods with higher protein and lower sugar—like protein shakes or high-protein frozen meals—over sugary snacks.
Many ‘high-protein’ UPFs use artificial sweeteners or additives; check labels for hidden ingredients.
medium confidenceWhy this study matters
Junk Food with More Protein = 196 Fewer Calories
In a controlled 54-hour trial, healthy young adults ate 196 fewer calories per day on a high-protein (30%) ultra-processed diet compared to a normal-protein (13%) ultra-processed diet—even though both diets were equally tasty, matched for fat and fiber, and served in unlimited amounts.
This flips the script: you don’t need to eat ‘healthy’ food to reduce calorie intake. Even packaged snacks can help you eat less if they’re higher in protein.
Your Body Burns 128 Extra Calories Just from Protein
The high-protein ultra-processed diet increased daily energy expenditure by 128 kcal—equivalent to a 30-minute walk—due to higher diet-induced thermogenesis from protein metabolism and increased glucagon-driven liver activity.
Most people think only exercise burns extra calories. This shows your body burns more just digesting protein—even when you’re sitting still.
Hormones Tell You to Stop Eating—Even on Junk Food
The high-protein diet increased satiety hormones PYY and glucagon by up to 30% and suppressed ghrelin (the hunger hormone), suggesting protein triggers biological signals to reduce appetite—even in ultra-processed foods.
It’s not about willpower—it’s biology. Your body naturally regulates intake when protein is high, even if the food is industrialized.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Even if the food is ultra-processed (like packaged snacks), eating more protein and less carbs makes your body burn more calories and feel fuller faster.
Research results
People ate 196 fewer calories per day, burned 128 more calories per day, and had a 14% better energy balance (less fat gain) on a high-protein ultra-processed diet.
What this means - more context
Yes — cutting 196 kcal/day is like skipping a small snack daily, which could lead to weight loss over time.
To determine whether a high-protein, lower-carbohydrate ultra-processed diet affects energy intake, expenditure, and balance in healthy young adults.
In a 54-hour single-blind crossover trial, 21 healthy young adults consumed two ultra-processed diets matched for palatability, fat, and fiber: a high-protein (30% energy), lower-carbohydrate (29% energy) diet (HPLC-UPF) and a normal-protein (13% energy), normal-carbohydrate (46% energy) diet (NPNC-UPF). The HPLC-UPF diet reduced energy intake by 196 kcal/day and increased energy expenditure by 128 kcal/day, improving energy balance from +32% to +18%. These changes were linked to increased satiety hormones (PYY, glucagon), suppressed ghrelin, and shifted macronutrient oxidation toward fat and protein use.
Methods Used
21 healthy young adults participated in a single-blind, randomized crossover trial. Diets were consumed ad libitum for 54 hours in a whole-room calorimeter. Diets were ultra-processed (84% of calories), matched for palatability, fat, fiber, and total calories, differing only in protein (30% vs 13%) and carbohydrate (29% vs 46%) content.
Main Finding
A short-term high-protein, lower-carbohydrate ultra-processed diet reduced daily energy intake by 196 kcal and increased energy expenditure by 128 kcal, leading to a 14-percentage-point improvement in energy balance (from +32% to +18%).
Confidence Level
High. Randomized crossover design, controlled environment (whole-room calorimeter), pre-registered, matched diet parameters, and direct measurement of energy intake/expenditure.
Study Flags
Red Flags
- •Short duration (54 hours) limits long-term relevance
- •Small sample size (n=21)
- •Only healthy young adults — results may not generalize to older or obese populations
Surprising Findings
Gastric emptying was faster on the high-protein diet, yet people ate less.
Common belief is that slower digestion = more fullness. But here, faster gastric emptying with high protein still led to reduced intake—challenging the idea that protein works by delaying stomach emptying.
Practical Takeaways
Swap one daily ultra-processed snack (e.g., chips or granola bar) for a high-protein version (e.g., protein bar, high-protein yogurt) to reduce daily calorie intake by ~200 kcal.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 578 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
High probability
on the GRADE evidence scale
This study is like a fair test where 21 people ate two different kinds of ultra-processed meals for a few days, and scientists measured exactly how much they ate and how many calories they burned. It shows that one kind of meal made them eat less and burn more — so we can say this diet caused those changes in the short term.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Randomized crossover design with within-subject comparison
- Controlled environment (whole-room calorimeter)
- Direct measurement of energy intake and expenditure
Weaknesses
- Single-blind (participants knew study was about protein content)
- Small sample size limits subgroup analyses and precision
- Short duration prevents conclusions about weight change or chronic effects
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Even if the food is ultra-processed (like packaged snacks), eating more protein and less carbs makes your body burn more calories and feel fuller faster.
Research results
People ate 196 fewer calories per day, burned 128 more calories per day, and had a 14% better energy balance (less fat gain) on a high-protein ultra-processed diet.
What this means - more context
Yes — cutting 196 kcal/day is like skipping a small snack daily, which could lead to weight loss over time.
To determine whether a high-protein, lower-carbohydrate ultra-processed diet affects energy intake, expenditure, and balance in healthy young adults.
In a 54-hour single-blind crossover trial, 21 healthy young adults consumed two ultra-processed diets matched for palatability, fat, and fiber: a high-protein (30% energy), lower-carbohydrate (29% energy) diet (HPLC-UPF) and a normal-protein (13% energy), normal-carbohydrate (46% energy) diet (NPNC-UPF). The HPLC-UPF diet reduced energy intake by 196 kcal/day and increased energy expenditure by 128 kcal/day, improving energy balance from +32% to +18%. These changes were linked to increased satiety hormones (PYY, glucagon), suppressed ghrelin, and shifted macronutrient oxidation toward fat and protein use.
Methods Used
21 healthy young adults participated in a single-blind, randomized crossover trial. Diets were consumed ad libitum for 54 hours in a whole-room calorimeter. Diets were ultra-processed (84% of calories), matched for palatability, fat, fiber, and total calories, differing only in protein (30% vs 13%) and carbohydrate (29% vs 46%) content.
Main Finding
A short-term high-protein, lower-carbohydrate ultra-processed diet reduced daily energy intake by 196 kcal and increased energy expenditure by 128 kcal, leading to a 14-percentage-point improvement in energy balance (from +32% to +18%).
Confidence Level
High. Randomized crossover design, controlled environment (whole-room calorimeter), pre-registered, matched diet parameters, and direct measurement of energy intake/expenditure.
Study Flags
Red Flags
- •Short duration (54 hours) limits long-term relevance
- •Small sample size (n=21)
- •Only healthy young adults — results may not generalize to older or obese populations
Surprising Findings
Gastric emptying was faster on the high-protein diet, yet people ate less.
Common belief is that slower digestion = more fullness. But here, faster gastric emptying with high protein still led to reduced intake—challenging the idea that protein works by delaying stomach emptying.
Practical Takeaways
Swap one daily ultra-processed snack (e.g., chips or granola bar) for a high-protein version (e.g., protein bar, high-protein yogurt) to reduce daily calorie intake by ~200 kcal.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 578 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
High probability
on the GRADE evidence scale
This study is like a fair test where 21 people ate two different kinds of ultra-processed meals for a few days, and scientists measured exactly how much they ate and how many calories they burned. It shows that one kind of meal made them eat less and burn more — so we can say this diet caused those changes in the short term.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Randomized crossover design with within-subject comparison
- Controlled environment (whole-room calorimeter)
- Direct measurement of energy intake and expenditure
Weaknesses
- Single-blind (participants knew study was about protein content)
- Small sample size limits subgroup analyses and precision
- Short duration prevents conclusions about weight change or chronic effects
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
This study was very well done because everyone ate the same meals in a special room that measured every calorie, and they didn’t know which meal was which. But it only lasted a few days and only included young, healthy people — so we can’t say it works for everyone or for a long time.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
70 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=21)+2.0/20
- Follow-up+10/10
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 577 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Limited to short-term effects in healthy young adults; cannot generalize to long-term outcomes, older populations, or those with metabolic disease.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding disclosures were reported in the study text.
The study lacks any declared funding source, conflict of interest statement, or author affiliations with industry. While the absence of disclosure raises a general transparency concern, there is no evidence of actual conflict or industry influence in the reported methods or results.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
3 videos from 3 different creators cite this study, drawing 3 claims from it.
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
- Strong evidence
At least some randomized or controlled trials support this claim.
Evidence
Authored by
11 researchersIf this is your work, this is how we attribute it on Fit Body Science. Franziska Anna Hägele is listed as the lead author.
- Anja Bosy‐WestphalCorresponding
Cited in 4 claims