Cutting ultra-processed food
Two randomized feeding trials show that people eat more and lose less weight on ultra-processed diets, even when the menus are matched for nutrients or meet healthy-eating guidelines. Swapping most ultra-processed products for minimally processed foods is a practical way to eat fewer calories without counting every one, though the exact reason it works is still unclear.
What the science says
- Ultra-processed diets drive overeating Moderate evidence
In Hall et al.'s 2019 inpatient crossover trial, 20 adults ate as much as they wanted of ultra-processed or unprocessed diets matched for calories offered, energy density, sugar, fat, fibre and sodium. They ate about 500 kcal/day more on the ultra-processed diet, gaining 0.9 kg in two weeks, and lost 0.9 kg on the unprocessed diet. It was a small, short study, but tightly controlled.
- Even guideline-compliant ultra-processed diets lose less Moderate evidence
In Dicken et al.'s 2025 crossover trial, 55 adults ate two 8-week diets that both followed the UK healthy-eating guide, one minimally processed and one ultra-processed. Both caused weight loss, but the minimally processed diet produced about twice as much (−2.1% vs −1.1% of body weight).
- High intake is linked to obesity and disease in observational studies Moderate evidence
Lane et al.'s 2024 umbrella review of 45 pooled analyses covering almost 10 million people found higher ultra-processed food intake associated with higher risks of 32 health outcomes, including cardiovascular death and type 2 diabetes. These studies are observational, and the certainty of many associations was rated low or very low, so they show links, not proof of cause.
- Why it happens is not settled Limited evidence
Neither Hall et al. nor Dicken et al. identified the exact mechanism; candidates include faster eating, higher palatability and lower satiety. The ultra-processed category is also broad, so it is not established that every ultra-processed product affects weight equally.
How to apply it
Build most meals from minimally processed foods, keep a few convenient processed staples that fit your calories, and treat ultra-processed snacks and drinks as planned extras rather than defaults.
Who should be careful
Cutting ultra-processed food is safe for healthy adults, but avoid turning it into rigid rules about 'clean' foods if you have a history of eating disorders; work with a physician, psychologist or registered dietitian instead. People with diabetes, kidney disease, food allergies, or who are pregnant should plan diet changes with a physician or registered dietitian. Anyone considering weight-loss medication should discuss it with a physician; this page gives no drug advice.
Frequently asked questions
Do ultra-processed foods really make you eat more?
In Hall et al.'s 2019 inpatient trial, people ate about 500 kcal/day more on an ultra-processed diet than on an unprocessed one with matched nutrients, and gained 0.9 kg in two weeks.
If my ultra-processed foods are 'healthy', does it still matter?
It seems to. In Dicken et al.'s trial, both diets met UK healthy-eating guidelines, yet the minimally processed version produced about twice the weight loss over 8 weeks.
Do I have to eliminate ultra-processed food completely?
No. The trials compared mostly processed with mostly unprocessed diets; a practical target is keeping ultra-processed food to under about 20–30% of calories and building most meals from minimally processed foods.
Scientific references
- Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake
- Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health: a randomized, crossover trial
- Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses
More on weight loss
- Calorie deficit Strong evidence
Fat loss requires eating fewer calories than you burn for weeks to months; every diet that works does this, whatever it is called.
- Rate of weight loss Moderate evidence
For people who lift, losing about 0.
- High-protein diet while dieting Strong evidence
Eating more protein during a calorie deficit helps keep lean mass and gives a small extra fat loss compared with a standard-protein diet of the same calories.
- Resistance training while dieting Strong evidence
Lifting weights during a diet makes much more of the weight you lose come from fat instead of muscle, and it keeps or raises strength.
- Cardio for weight loss Moderate evidence
Cardio helps fat loss, but at typical doses it produces only a couple of kilograms on its own; clinically meaningful loss takes high volumes (more than about 250 minutes a week) or a calorie deficit alongside it.
- Diet breaks and refeeds Moderate evidence
Planned periods at maintenance calories in the middle of a diet are at least as effective as dieting continuously and may make the diet easier to tolerate.