Myth #1: The 8-By-8 Water Rule

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  Health and Fitness on Sat, Nov 22nd, 2025 by CNET

Stop believing these 18 health myths that are completely false

Health information has never been more abundant – and unfortunately, not all of it is accurate. From the “always drink eight glasses of water a day” mantra to the age‑old fear that dairy will damage your bones, many popular claims are based on misinformation, outdated science or simply misunderstandings. A recent CNET article, “Stop believing these 18 health myths that are completely false,” takes a hard look at the most common misconceptions and explains why they’re wrong, backing every claim with reputable sources and evidence from medical research. Below is a concise rundown of those myths, why they’re misleading, and what you should actually do to stay healthy.

1. You must drink eight glasses of water every day.

The “8‑by‑8” rule (eight 8‑oz glasses) is a convenient guideline, but it’s a myth that underestimates how fluid needs vary by age, activity level, climate, and diet. The Institute of Medicine recommends about 3.7 L for men and 2.7 L for women, including all beverages and food moisture. In hot climates or during heavy exercise, fluid loss can be far higher. A better approach is to listen to your body – thirst, urine color, and overall hydration status – rather than rigidly sticking to a glass count.

2. Skipping meals or eating “only when hungry” is the best way to lose weight.

Contrary to popular belief, meal timing isn’t the key determinant of weight loss. Weight loss depends on energy balance – calories in versus calories out – rather than the frequency of meals. Research from the American Journal of Clinical Nutrition shows that as long as total caloric intake stays below expenditure, meal skipping or spacing does not confer additional benefits. Skipping meals can also lead to overeating later and negatively affect blood glucose control.

3. All carbs are bad.

Carbohydrates are the body’s main fuel source, and not all carbs are created equal. Complex carbohydrates—found in whole grains, fruits, vegetables, and legumes—provide fiber, vitamins, and minerals and are linked to lower risk of heart disease. The 2020 Dietary Guidelines for Americans, endorsed by the USDA and the HHS, emphasize the importance of a balanced intake of complex carbs while limiting refined sugars.

4. Dairy is harmful to bone health.

Dairy’s reputation as a bone‑builder has been challenged by recent studies. A 2019 review in Nutrients found that while dairy provides calcium and vitamin D, excessive protein (often found in dairy) can increase calcium excretion, and calcium‑rich plant foods can provide comparable benefits without the added saturated fats. Instead, focus on a varied diet rich in calcium, vitamin D, and other bone‑supporting nutrients.

5. Caffeine on an empty stomach will kill your appetite and help you lose weight.

Caffeine does increase metabolic rate slightly, but consuming it on an empty stomach can spike cortisol and insulin, potentially leading to cravings and weight gain. A review in Obesity Reviews concluded that caffeine’s effect on appetite is modest at best and highly individual. If you’re trying to manage hunger, pair caffeine with a balanced meal or snack.

6. Eating before bed automatically leads to weight gain.

Weight gain is primarily a result of a caloric surplus over time, not the timing of those calories. A 2020 meta‑analysis in Sleep Medicine found no conclusive evidence linking nighttime eating to obesity. However, late‑night meals can disrupt sleep quality, which in turn can influence metabolism. Aim for light, balanced snacks if you’re hungry before bed.

7. Cold weather causes colds.

Respiratory viruses spread more readily in winter, but the cold itself doesn’t cause a cold. The Centers for Disease Control and Prevention (CDC) notes that viruses like the rhinovirus are more stable in cooler temperatures, and close indoor contact increases transmission. Staying warm, washing hands, and avoiding crowds are the real defenses against the common cold.

8. Vaccines cause autism.

This claim originated from a 1998 paper that has since been fully retracted, and large epidemiological studies have repeatedly found no link between vaccines and autism. The CDC, WHO, and the American Academy of Pediatrics all affirm that vaccines are safe and vital for preventing infectious diseases.

9. Soy protein eliminates “bad” cholesterol (LDL).

While soy protein can modestly lower LDL cholesterol, it is not a silver bullet. The American Heart Association recommends focusing on a heart‑healthy diet, including nuts, seeds, whole grains, and fish, and maintaining an active lifestyle. Soy can be part of a balanced diet, but relying solely on it to reduce LDL can be misleading.

10. Sugar causes hyperactivity in children.

A classic myth perpetuated by parents, teachers, and media. A 2007 systematic review in Pediatrics found no causal link between sugar intake and hyperactivity. The real drivers of behavioral changes are likely environmental (e.g., the excitement of a party) and psychosocial rather than sugar itself.

11. All fats are bad.

Fats are essential for hormone production, nerve function, and absorption of fat‑soluble vitamins. Unsaturated fats—found in olive oil, nuts, and fatty fish—are heart‑healthy, whereas saturated and trans fats should be limited. The American Heart Association recommends replacing saturated fats with unsaturated ones whenever possible.

12. You can’t get enough vitamin D from sun exposure alone.

Vitamin D synthesis is strongly influenced by latitude, skin pigmentation, sunscreen use, and time of day. The NIH states that moderate sun exposure (10–15 min a few times a week) can provide sufficient vitamin D for many people, but supplementation may still be necessary for those at higher risk of deficiency, such as the elderly or those living in northern climates.

13. Eating late at night increases heart‑disease risk.

A 2021 study in Heart showed that the time of eating can influence metabolic parameters, but the primary driver is overall caloric intake. A well‑timed, moderate dinner paired with regular exercise mitigates cardiovascular risk more effectively than worrying about the exact clock time.

14. All “natural” foods are healthy.

“Natural” does not automatically mean safe or nutritious. Organic produce may contain fewer pesticide residues, but it can still carry harmful microbes if improperly handled. A balanced diet rich in varied whole foods—both natural and minimally processed—is key.

15. Supplements can replace a balanced diet.

While certain nutrients—like vitamin D, omega‑3s, and iron—can benefit from supplementation, most people get adequate nutrition from a varied diet. The NIH warns that taking high doses of vitamins and minerals can lead to toxicity and interfere with medication efficacy.

16. Sitting for long periods is harmless if you exercise regularly.

Research from JAMA Internal Medicine indicates that prolonged sedentary behavior is an independent risk factor for cardiovascular disease and all‑cause mortality, even among those who meet aerobic activity guidelines. Short, frequent breaks for standing or walking can substantially reduce these risks.

17. “Detox” diets cleanse your body of toxins.

The human body is equipped with highly efficient detoxification systems: the liver, kidneys, lungs, and skin. A 2018 review in Clinical Nutrition found no evidence supporting the claim that fad detox diets have any real effect on toxin removal. In fact, extreme diets can deprive you of essential nutrients.

18. You need to eat before every workout.

While pre‑exercise nutrition can enhance performance, it’s not mandatory for all workouts. A 2018 study in Sports Medicine found that well‑timed protein and carbohydrate intake is beneficial mainly for endurance and strength training, but short, light workouts can be done on an empty stomach without adverse effects. Focus on hydration and overall nutrient status instead.

Putting It All Together

The truth is that healthy living hinges on evidence‑based habits, not on simplistic “rules” that are often handed down through anecdote or old wives’ tales. By debunking these 18 myths, the CNET article reminds us to look at the science behind the claim, ask how the recommendation aligns with your personal health goals, and consult trusted resources such as the CDC, NIH, and peer‑reviewed journals. Whether it’s recalibrating your fluid intake, revising your approach to fats, or debunking the vaccination‑autism link, the takeaway is simple: knowledge is power—and it’s time to replace misinformation with fact‑based decisions.