Deja-Food: Explaining an Underappreciated Process in Weight Loss and Practical Solutions to Fix This

Weight loss ought to be straightforward: calories in, calories out. Track what you eat, maintain a 500-calorie deficit per day, and you should lose a pound a week. Simple, right?

But then it doesn’t work. You tracked every morsel, every step, and still—no weight loss. Or worse: you gained weight. What’s going on? Let’s break it down.

1. People underestimate how much they eat—especially portion sizes.

2. People forget that they’ve eaten altogether—what we might call "Foodmnesia."

3. People underestimate the calories in the foods they do remember.

4. Larger meals lead to greater underestimation of total intake.

5. Eating while distracted worsens this:

   • You disconnect from taste and fullness cues.

   • You don’t form a strong memory of the meal, especially if you "hide the evidence."

6. People overestimate how much they exercise.

7. They overestimate how many calories they’ve burned.

8. They then eat back those imaginary calories.

9. They trust fitness trackers, which routinely overestimate calorie burn.

Representative Studies

A BMJ study (Block et al., 2013) found that people consistently underestimated the calorie content of fast-food meals—by an average of 175 kcal. Larger meals led to even greater misjudgment. Shockingly, nearly a quarter of participants underestimated by 500 kcal or more, highlighting just how far off people can be when estimating intake.

Duif et al. (2020) used fMRI to show that distraction during eating weakens connectivity between brain regions responsible for processing taste and integrating it with reward. Those with the most disrupted connectivity ate more afterward, suggesting that distracted eating can impair satiety and lead to overeating.

Robinson et al. (2013) reviewed 24 studies and found that distracted eating not only increased immediate intake (SMD ≈ 0.39), but also had a strong effect on later intake (SMD ≈ 0.76). People forgot they'd eaten and ate more later. The review emphasized that memory and attention are central to appetite regulation.

King et al. (2009) showed that people overestimate calories burned during exercise by 3–4× and then overeat afterward, undermining their deficit.

Shcherbina et al. (2017) found that fitness trackers overestimate calorie burn by 27% to 93%, further compounding the illusion of a calorie deficit.

Practical Fixes

1. Weigh your food with a scale—not by volume. Volume can be imprecise and if I’m motivated I stuff a heck of a lot of marshmallows in a tight space. Even if you don’t weigh your food every time, doing it calibrates your internal food meter and improves your ability to estimate your portions when you are “in the wild.”

2. Cognitive Load and Decision Fatigue: When mental resources are depleted—like after a stressful day—we're more prone to make poor eating decisions. Plan what you’re going to eat ahead of time, especially if you know you’re going to be tired, hungry, lonely, or angry—when you're more likely to eat with your eyes, not your brain.

3. Track what you eat, whether on paper or digitally. Logging increases awareness and accountability.

4. Use reputable programs to estimate food calories. You’ll be surprised by how calorie-dense some foods are.

5. Limit eating out—it’s nearly impossible to track accurately.

6. Eat back only half of the first 500 calories your fitness tracker claims you burned. After that, use discretion.

7. Practice Hara Hachi Bu—the Japanese principle of eating until you’re 80% full. It cultivates mindfulness and prevents overeating.

8. Acknowledge Non-Linearity: Even when everything is tracked perfectly, the scale may not move predictably. Water retention, glycogen storage, and hormone fluctuations all introduce noise. Stay focused on long-term trends and non-scale victories like clothing fit, energy, and consistency.

9. Emphasize Consistency Over Perfection: One indulgent meal won’t derail progress—quitting will. Sustainable weight loss is built on being consistently “good enough,” not perfect.

Bon Appetit.

References

Block, J. P., Condon, S. K., Kleinman, K., Mullen, J., Linakis, S. K., Rifas-Shiman, S., & Gillman, M. W. (2013). Consumers’ estimation of calorie content at fast food restaurants: Cross sectional observational study. BMJ, 346, f2907. https://doi.org/10.1136/bmj.f2907

Duif, I., Wegman, J., Mars, M. M., de Graaf, C., Smeets, P. A. M., & Aarts, E. (2020). Effects of distraction on taste-related neural processing: A cross-sectional fMRI study. The American Journal of Clinical Nutrition, 111(3), 546–555. https://doi.org/10.1093/ajcn/nqaa032

King, N. A., Hopkins, M., Caudwell, P., Stubbs, R. J., & Blundell, J. E. (2009). Individual variability following 12 weeks of supervised exercise: identification and characterization of compensation for exercise-induced weight loss. International Journal of Obesity, 32(1), 177–184. https://doi.org/10.1038/sj.ijo.0803773

Robinson, E., Aveyard, P., & Higgs, S. (2013). Eating attentively: A systematic review and meta-analysis of the effect of food intake memory and awareness on eating. The American Journal of Clinical Nutrition, 97(4), 728–742. https://doi.org/10.3945/ajcn.112.045245

Shcherbina, A., Mattsson, C. M., Waggott, D., Salisbury, H., Christle, J. W., Hastie, T., & Ashley, E. A. (2017). Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. Journal of Personalized Medicine, 7(2), 3. https://doi.org/10.3390/jpm7020003