Ten claims that survive because they sound sensible. Each one is checked below against agency guidance and randomised trials — and where the debunking is usually overdone, that is said too. A myth being wrong does not make its opposite right.
The short version
- The clock does not add calories — but eating late does measurably increase hunger.
- Eating more often does not raise your metabolic rate. Skipping a whole meal moved resting metabolism by under 11 calories a day.
- Detoxes have no supporting research, and the FDA keeps finding hidden drugs in them.
- Spot reduction does not exist. Pooled across 1,158 people, the effect size was −0.03.
- Over 70% of sodium comes from packaged and restaurant food, not the salt shaker.
- There is no eight-glasses rule. The panel that set the reference values said so explicitly.
Myth 1: “Eating after 8 pm makes you gain weight”
The clock has no calories in it. But the honest version is more interesting than a flat debunk.
A tightly controlled crossover trial fed people identical meals four hours apart in the day and measured what changed. Late eating “increased hunger (p < 0.0001)”, raised the ghrelin-to-leptin ratio, decreased waketime energy expenditure and shifted fat-tissue gene expression toward storage. Sixteen people, so treat it as a signal rather than a settled fact.
MedlinePlus lands in the same place from the other direction, noting that people who eat late at night do tend to put on weight — and attributing it to what gets eaten late and to poor sleep, rather than to the hour itself.
Myth 2: “Eating six small meals boosts your metabolism”
A 2023 systematic review of eating frequency found “no difference between high- and low-frequency eating for weight-change (MD: −0.62 kg, CI95: −2.76 to 1.52 kg, p = 0.57)”, no fat-mass difference, and “no discernible advantage to eating in a high- or low-frequency dietary pattern for cardiometabolic health.”
An earlier meta-analysis of 15 studies initially showed a benefit for higher frequency — until sensitivity analysis showed “the positive findings were the product of a single study.”
And the scale of the supposed effect is worth seeing. In a six-week trial where one group ate a full breakfast and the other ate nothing until noon, resting metabolic rate stayed stable within 11 kcal a day. An entire meal moved the needle by less than a bite.
One honesty note. The 2023 review flags that 15 of its 16 trials were at high risk of bias. So the correct claim is “no evidence of a benefit,” not “proven to make no difference.” Meal frequency is a preference, not a lever.
Myth 3: “A detox or cleanse clears out toxins”
The National Center for Complementary and Integrative Health has looked: “There was no compelling research to support the use of ‘detox’ diets for weight management or eliminating toxins from the body.” The research that exists has design flaws, small samples and often no peer review. Any weight lost comes from eating very little, and returns.
The safety side is not theoretical either. NCCIH lists unpasteurised juices carrying harmful bacteria, kidney-stone risk from high-oxalate cleanse foods, dehydration and malnutrition from laxative-driven diarrhoea, and dangerous electrolyte imbalances from extreme fasting.
And there is a live regulatory example. A product sold as “Detoxi Slim” was found by the FDA to contain sibutramine — a drug withdrawn from the US market in 2010 that can substantially increase blood pressure and heart rate. It was not on the label.
Myth 4: “Skipping breakfast makes you fat”
A 2019 review in The BMJ pooled 13 randomised trials and found the opposite of the folk wisdom: people assigned to eat breakfast ended up 0.44 kg heavier and ate about 260 more calories a day. A separate 16-week trial in 309 adults trying to lose weight found that a recommendation to eat or skip breakfast changed habits but “had no discernable effect on weight loss.”
Do not flip this into “breakfast is a myth.” The BMJ authors themselves warn that most included studies were low quality. And the six-week controlled trial found that breakfast eaters did about 442 more calories a day of spontaneous physical activity and had steadier afternoon and evening blood glucose. The narrow, defensible claim: adding breakfast is not an effective weight-loss instruction. That is not the same as breakfast being useless.
Myth 5: “Crunches burn belly fat”
Spot reduction has now been tested properly. A meta-analysis of 13 high-quality studies covering 1,158 participants and 37 comparisons — typically training one limb and comparing it against the untrained one — found a pooled effect size of −0.03, p = 0.508.
Its conclusion: “Localized muscle training had no effect on localized adipose tissue depots, i.e., there was no spot reduction” — regardless of population or exercise type. The authors attribute the belief’s persistence to “wishful thinking and convenient marketing strategies.” Training a muscle builds that muscle. Where fat comes off is not yours to choose.
Myth 6: “Eggs will raise your cholesterol”
The American Heart Association’s science advisory on dietary cholesterol notes that observational evidence “generally does not indicate a significant association with cardiovascular disease risk” — while also noting that intervention studies do associate cholesterol intakes above current average levels with higher LDL.
Its resolution is to stop chasing a number: “guidance focused on dietary patterns is more likely to improve diet quality and to promote cardiovascular health.” In practical terms the AHA’s summary allows healthy people up to one whole egg or equivalent daily, with different advice for people who have dyslipidaemia or diabetes.
Myth 7: “Put down the salt shaker”
The shaker is not where your sodium comes from. The FDA states that over 70% of sodium comes from “packaged and prepared foods—not from table salt added to food when cooking or eating.”
| Figure | Amount |
|---|---|
| Average US intake | About 3,400 mg a day (FDA); more than 3,300 mg (CDC) |
| Recommended limit | Less than 2,300 mg a day — about one teaspoon of table salt |
| Where it comes from | Deli sandwiches, soups, pizza, poultry, savoury snacks, pasta dishes, bread, cheese |
Bread is on that list not because it is salty but because people eat a lot of it. That is the whole point: cutting sodium is a shopping decision, not a table-manners one. Our sodium intake guide covers the swaps.
Myth 8: “Gluten-free is healthier”
The NIDDK addresses this directly: “researchers have found no evidence that a gluten-free diet promotes better health or weight loss for the general population.”
It also names two costs. Avoiding gluten without guidance risks not getting enough fibre, iron and calcium. And “some packaged gluten-free foods may be higher in fat and sugar than the same foods that contain gluten.”
For the roughly 2 million people in the United States with celiac disease, a gluten-free diet is lifelong and medically necessary. For everyone else it is a shopping preference with a nutritional downside.
Myth 9: “Drink eight glasses of water a day”
The panel that set the US reference values for water addressed this in the announcement itself: “We don’t offer any rule of thumb based on how many glasses of water people should drink each day.”
What it did give is total water — from all drinks and all food — of about 2.7 litres a day for women and 3.7 litres for men, with roughly 20% of that coming from food. It also noted that “the vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide,” and that caffeinated drinks count toward the total.
Drinking far beyond thirst is not harmless: exercise-associated hyponatremia — blood sodium below 135 mmol/L — is a documented, life-threatening consequence of overdrinking during activity.
Myth 10: “Green tea burns fat”
A Cochrane review pooled trials in 1,945 participants. Outside Japan-based studies, the pooled weight change was −0.04 kg (95% CI −0.5 to 0.4), and the reviewers concluded the loss “was statistically not significant, was very small and is not likely to be clinically important.”
NCCIH allows that catechins and caffeine “may have a modest effect on body weight” — and adds a caution that belongs with it: “liver injury has been reported in some people who used green tea products, primarily green tea extracts in tablet or capsule form.” Drinking tea is fine. Buying concentrated extracts for fat loss buys a risk in exchange for an effect too small to notice.
FAQ
Does eating late at night actually matter?
Not because of the clock. Under tightly controlled conditions, late eating increased hunger and lowered daytime energy expenditure — so it may make eating less harder, rather than adding calories on its own.
Is it bad to skip breakfast?
Trials do not support eating breakfast as a weight-loss strategy; assigned breakfast eaters ate more and weighed slightly more. But breakfast eaters in one controlled trial moved considerably more during the day, so “skip it” is not automatically better either.
Do detox teas work?
No compelling research supports them, the weight lost is from eating almost nothing, and the FDA has repeatedly found undeclared prescription drugs in products in this category.
How can I lose fat from my stomach specifically?
You cannot direct it. Pooled across 13 studies, localised training had no effect on localised fat. Overall energy balance decides how much comes off; genetics decide the order.
How much water do I actually need?
About 2.7 litres of total water a day for women and 3.7 for men, including what comes from food and from all drinks — with thirst as an adequate guide for most healthy people.
Where this fits
The training-specific counterpart — the anabolic window, protein ceilings, creatine, BCAAs and fasted cardio — is in sports nutrition myths. For the words on packages that create half of these beliefs, see what food label claims legally mean.
Every figure here is linked to its source in the text: the FDA, the CDC, the NIDDK, the National Center for Complementary and Integrative Health, the National Academies, the American Heart Association, MedlinePlus, and peer-reviewed reviews and trials in The BMJ, Nutrition Reviews, Cochrane, Cell Metabolism, the American Journal of Clinical Nutrition, Circulation and Human Movement. Checked against those sources on 2 September 2026. Educational information, not medical advice — see our medical disclaimer.
This content is for educational purposes only and is not medical advice. Always consult a qualified healthcare professional for personalised guidance.
