Black-and-white thinking predicts regained weight, so learn to think in “mostly”

Key takeaways

• In a 2004 study of 54 women who had lost weight at slimming clubs, black-and-white thinking was one of two factors that predicted who regained weight over the next year.
• In data from more than 54,000 weight-loss program users and 1,838 randomly chosen West German residents, flexible eating rules went with lower body weight and less binge eating, while rigid rules went with the opposite.
• In a focus-group study released in January 2026, adults who struggled to keep exercising described skipping a workout entirely when their planned routine fell through, rather than doing a shorter version.
• Federal guidelines say any amount of physical activity has some health benefit, and short bouts count toward your weekly goal.
• You can practice “mostly” thinking in five minutes on paper: catch the absolute word, find the middle ground and pick the next small step.

In a study announced in January 2026, researchers from the University of Michigan and Kent State University held focus groups with 27 adults¹. Everyone in the groups had tried to exercise regularly and kept stopping.

One participant said a workout shorter than 15 minutes didn’t count as exercise at all, even if it was made up of all-out sprints¹. Others described the same pattern. When their planned routine stopped being workable, they didn’t shrink the workout. They skipped it¹.

The researchers called it all-or-nothing thinking. The same habit of mind shows up with food. In a study from the University of Oxford, women who had just lost weight were followed for a year. Black-and-white thinking was one of two factors that predicted who regained².

Natural-health values can feed this trap without anyone meaning to. Words like clean, pure and toxic sort foods into saints and sinners, and a single “slip” can feel like a moral failure. Your values give you direction. The goal is to hold them in a way that survives a birthday party, a sick week or a tight budget.

This article explains what the research shows, where it’s thin, and how to practice thinking in “mostly.”

Cognitive therapists named this trap long ago

Cognitive behavioral therapy, or CBT, is a talk therapy that teaches people to notice and test their automatic thoughts. Therapists who use it work from lists of common thinking traps, called cognitive distortions.

All-or-nothing thinking, also called black-and-white thinking, is near the top of most lists. The Department of Veterans Affairs uses a list adapted from Dr. David Burns’s 1989 book, The Feeling Good Handbook³. It describes the trap as treating anything less than perfect as a total failure³.

The Beck Institute for Cognitive Behavior Therapy lists it on its published thought record worksheet⁴. That worksheet carries a useful reminder: a thought can be completely true, completely false, or somewhere in the middle⁴.

In health, the trap sounds like this. “I missed Monday’s workout, so this week is shot.” “I had fries, so I’m off my plan.” “If I can’t afford all organic, why bother?” Each one turns a partial result into a zero.

Black-and-white thinking tracks with regained weight

Some of the clearest research comes from an Oxford team: Byrne, Cooper and Fairburn. First, they interviewed 76 women⁵. Twenty-eight had lost weight and kept it off for at least a year, 28 had regained it, and 20 had a stable, healthy weight⁵.

What set the regainers apart? Many judged their worth by their weight and shape, and many turned to food to cope with their moods. They had missed the weight goals they set, were unhappy with the results and kept a looser eye on their weight. Their thinking also ran in black and white⁵.

Interviews can only show a link. The team’s next study followed women forward in time². It tracked 54 women who had just lost 10% of their body weight at community slimming clubs, checking in every two months for a year. Two factors predicted who regained: black-and-white thinking and the highest weight a woman had ever reached².

A 2015 online survey of 241 adults by researchers at Wageningen University pointed the same way⁶. Black-and-white beliefs about food helped explain why strict dieting went along with regaining weight⁶.

These are small studies, mostly of women, and none can prove that changing your thinking prevents regain. Our article on correlation and causation explains why. Still, the pattern has held across different designs, which is why we rate it promising but early.

Rigid food rules tend to break; flexible ones bend

Researchers who study dieting draw a line between two styles of self-control. Rigid control is a very black-and-white approach to food: foods are allowed or forbidden, and you’re on the diet or off it⁸. Flexible control allows all foods in reasonable amounts and adjusts as you go⁸.

In 1999, Westenhöfer and colleagues tested these two styles in large groups⁷. They used data from 54,517 people in a computer-assisted weight-loss program and a survey of 1,838 randomly chosen residents of West Germany⁷.

The two styles pointed in opposite directions. People who leaned flexible tended to weigh less for their height, binged less often and were more likely to lose weight during the year-long program⁷. People who leaned rigid tended to have a higher body mass index (BMI), a measure of weight for height, and they binged more often and more severely⁷.

A lab experiment adds a clue about why. Since the 1970s, researchers have reported that some chronic dieters eat more, not less, after being served a rich “preload” food⁹¹⁰. A 1981 study concluded that this pattern depends partly on what dieters think they’re eating, not only on the food itself⁹.

Westenhoefer’s team tested this in 1994 with 133 young women¹⁰. Some drank a 200-milliliter milkshake before tasting ice cream, and some didn’t. Flexible eaters ate less ice cream after the milkshake, as you’d expect. Rigid eaters ate about the same either way¹⁰.

The classic overeating effect hasn’t shown up in every study. In this one, it appeared only in women who scored high on both strict dieting and a general tendency to overeat¹⁰.

Put simply, a rigid rule has no middle setting. Once it’s broken, there’s little reason to hold back. Flexible eaters treated the milkshake as part of the day and adjusted.

You can rewrite a rigid rule with three parts: a range, a planned exception and a restart point. “No sugar, ever” might become “Dessert two evenings a week, enjoyed without guilt, and the next meal is a normal meal.” That’s a practical idea built on this research, not a tested formula.

Calling foods “good” or “bad” may backfire

Many people believe guilt keeps them on track. One study suggests it doesn’t.

Roeline Kuijer and Jessica Boyce asked adults whether they linked chocolate cake with guilt or with celebration, then followed them over time¹¹. Guilt brought no clear benefit to motivation¹¹. People who chose guilt felt less in control of their eating and kept their weight steady less well over 18 months¹¹. Among those trying to lose weight, the guilt group lost less over three months¹¹.

This is one study showing associations, and it can’t prove guilt caused the difference. But it fits the rest of the research. Moral labels make every food choice a pass-or-fail test.

A gentler habit is to describe foods by what they do for you. “This keeps me full,” “this is a treat I love,” and “this doesn’t sit well with me” are all honest. None of them turns one dessert into a verdict on your character.

The same trap empties the gym

The Michigan and Kent State study mapped how all-or-nothing thinking works with exercise¹. Its participants, aged 19 to 79, described a mindset with four strands.

Only a “real” workout of the right length or intensity counted. Exercise felt optional, the first thing to drop when the day filled up. People went hunting for reasons to skip, such as effort, pain or discomfort. And many were puzzled about why they kept quitting, since they had enjoyed exercise before¹.

Study author Michelle Segar, a University of Michigan behavioral scientist, suggests dropping the self-blame and choosing “good enough” over perfect¹. Focus groups can reveal a pattern, but they can’t say how common it is, so treat these findings as a first look.

Federal guidelines already back the “good enough” approach. The current, second edition of the Physical Activity Guidelines for Americans says “any amount of physical activity has some health benefits”¹². It also dropped an older rule that activity had to come in bouts of at least 10 minutes to count¹².

The weekly target for adults is still 150 to 300 minutes of moderate activity, plus muscle-strengthening on at least two days¹². But a 10-minute walk on a hectic day is progress toward it, not a failure to reach it.

Partial credit is real credit

All-or-nothing thinking often travels with perfectionism. In a 2007 study from Curtin University in Australia, covering 252 people in clinical treatment, athletes and students, black-and-white thinking was the strongest predictor of the distressing kind of perfectionism¹³.

The math of health rarely works like a pass-or-fail test. A 2008 analysis in the BMJ pooled 12 long-term studies with more than 1.5 million people¹⁴. Researchers scored how closely people ate a Mediterranean-style diet. Each two-point rise on the score went with a 9% lower risk of death during follow-up¹⁴.

The analysis measured benefit for each step up the scale, not as a pass-or-fail cutoff. These were observational studies, so they show a link, not proof. But the shape of the finding is the point: moving partway is worth something.

That’s the idea behind “mostly” rules of thumb, such as eating the way you want 80% of the time or moving on most days. They are practical heuristics, not tested formulas. Their value is that they leave room for real life without making it a failure.

A five-minute “mostly” thought record

CBT therapists ask clients to write their thoughts down, because a thought on paper is easier to test than one in your head³⁴. Here is a short version built for health habits. Do it when you notice the urge to quit or the words “ruined,” “always” or “never.”

1. Catch the thought. Write it down exactly as it showed up.
2. Rate it. How true does it feel, from 0 to 100?
3. Find what’s true. Write the part of the thought that is accurate.
4. Find what it leaves out. What went right today or this week? What’s the actual size of the slip?
5. Write the “mostly” version. Make it a sentence that is both accurate and kind.
6. Pick the next small step. Choose something you can do in the next few hours.
7. Rate the original thought again. If it dropped, the exercise worked.

The examples below are hypothetical, to show how it works.

The all-or-nothing thought	What’s true	What it leaves out	The “mostly” version	Next small step
“I had cake at the office party, so today is ruined.”	I ate more sugar than I planned.	Breakfast and lunch went the way I wanted. One slice is one slice.	“I ate the way I want most of today, plus cake I enjoyed.”	Have the dinner I planned.
“I can’t make my 45-minute class, so there’s no point.”	I’ll miss the class.	A short walk still counts toward my week.	“I’m active most days. Today is a short day.”	Walk 10 minutes after lunch.
“I couldn’t afford organic berries this week. I’m failing at eating clean.”	Money was tight.	Fresh fruit is still fruit, and most of my food matches my values.	“I’m eating mostly whole foods on a real budget.”	Rinse the berries and enjoy them.
________	______	______	______	______

What the evidence shows

Claim	Evidence rating	What it rests on
Black-and-white thinking predicts regaining lost weight	Promising but early	Two small Oxford studies of women and one online survey; observational256
Flexible eating rules work better than rigid ones	Promising but early	Large surveys and program data, plus a small lab study; associations, not trials710
Feeling guilty about treats keeps you on track	Evidence says no, or unsafe	Tested in one long-term study: guilt brought no benefit and went with worse weight outcomes; associations only11
All-or-nothing thinking leads people to skip exercise	Not enough evidence	One qualitative study of 27 adults; describes the pattern but not how common it is1
Some physical activity is better than none	Strong evidence	Federal guidelines state that any amount has some health benefits12
Partial improvements in diet bring partial benefits	Promising but early	Large observational meta-analysis showing a step-by-step link14
Writing down and testing thoughts reduces all-or-nothing thinking in daily health habits	Not enough evidence	Standard CBT practice, but we found no trials of this specific use34

Questions readers ask

The bottom line

All-or-nothing thinking turns a small slip into a reason to quit. Research links it to regained weight and abandoned exercise, and it finds that flexible rules hold up better than rigid ones. Most of that evidence is small and observational, but it points in one direction.

You don’t have to lower your standards to escape the trap. Hold your values as a direction, give your rules a range, and count partial credit. When the word “ruined” shows up, write it down, find the middle and take the next small step.

Related reading

• A healthy identity supports good habits, while all-or-nothing food rules work against them
• Old habits run on cues rather than willpower, and you can rewire them
• Chocolate tracks with Nobel prizes, and other lessons in telling a link from a cause
• “Clean” is a marketing category, not a safety standard
• A slip doesn’t erase your progress, but your reaction to it can

Sources

1. University of Michigan. “Why Your Plans to Workout Go Wrong” (news release on Segar M, Taber J, Updegraff J, McGhee-Dinvaut A, “The Secret Life of All-or-Nothing Thinking With Exercise: New Insights Into an Overlooked Barrier,” BMC Public Health, DOI 10.1186/s12889-025-25780-9). Futurity, January 20, 2026 (first published by the University of Michigan, January 7, 2026). futurity.org
2. Byrne SM, Cooper Z, Fairburn CG. “Psychological Predictors of Weight Regain in Obesity.” Behaviour Research and Therapy, 2004;42(11):1341-1356. pubmed.ncbi.nlm.nih.gov
3. U.S. Department of Veterans Affairs, Whole Health Library. Mirgain SA, Singles J. “Working With Pain-Related Thoughts.” Updated March 19, 2025. va.gov
4. Beck Institute for Cognitive Behavior Therapy. “Thought Record Worksheet.” 2018, adapted from Beck J, Cognitive Behavior Therapy: Basics and Beyond, 3rd ed. beckinstitute.org
5. Byrne S, Cooper Z, Fairburn C. “Weight Maintenance and Relapse in Obesity: A Qualitative Study.” International Journal of Obesity, 2003;27:955-962. nature.com
6. Palascha A, van Kleef E, van Trijp JCM. “How Does Thinking in Black and White Terms Relate to Eating Behavior and Weight Regain?” Journal of Health Psychology, 2015;20(5):638-648. research.wur.nl
7. Westenhöfer J, Stunkard AJ, Pudel V. “Validation of the Flexible and Rigid Control Dimensions of Dietary Restraint.” International Journal of Eating Disorders, 1999;26(1):53-64. reposit.haw-hamburg.de
8. Timko CA, Perone J. “Rigid and Flexible Control of Eating Behavior and Their Relationship to Dieting Status.” Eating and Weight Disorders, 2006;11(3):e90-e95. pubmed.ncbi.nlm.nih.gov
9. Woody EZ, Costanzo PR, Liefer H, et al. “The Effects of Taste and Caloric Perceptions on the Eating Behavior of Restrained and Unrestrained Subjects.” Cognitive Therapy and Research, 1981;5:381-390. link.springer.com
10. Westenhoefer J, Broeckmann P, Munch AK, Pudel V. “Cognitive Control of Eating Behaviour and the Disinhibition Effect.” Appetite, 1994;23(1):27-41. agris.fao.org
11. Kuijer RG, Boyce JA. “Chocolate Cake. Guilt or Celebration? Associations With Healthy Eating Attitudes, Perceived Behavioural Control, Intentions and Weight-Loss.” Appetite, 2014. altmetric.com
12. U.S. Office of Disease Prevention and Health Promotion. “Top 10 Things to Know About the Second Edition of the Physical Activity Guidelines for Americans.” Updated November 19, 2025. odphp.health.gov
13. Egan SJ, Piek JP, Dyck MJ, Rees CS. “The Role of Dichotomous Thinking and Rigidity in Perfectionism.” Behaviour Research and Therapy, 2007;45(8):1813-1822. pubmed.ncbi.nlm.nih.gov
14. Sofi F, Cesari F, Abbate R, Gensini GF, Casini A. “Adherence to Mediterranean Diet and Health Status: Meta-Analysis.” BMJ, 2008;337:a1344. flore.unifi.it
15. National Alliance for Eating Disorders. Helpline information (homepage). Accessed October 2026. allianceforeatingdisorders.com