Dr. Mindy Pelz

There is mechanistic evidence suggesting that caffeine can activate a cellular clean-up process, but the translation to everyday coffee consumption in healthy people has not yet been made. The specific time window of one to four hours is not supported by the research: no established threshold or timeline for coffee-induced autophagy in humans has been determined. The claim sounds more concrete than the evidence allows.

Multiple studies show that intermittent fasting improves insulin sensitivity and lowers fasting insulin levels, which supports the core of the claim. For blood pressure, the evidence is less direct in this context: studies point to broader cardiovascular benefits, but a specific effect on blood pressure independent of weight loss has not been firmly established. The crucial issue lies in calorie intake: a direct comparison between time-restricted eating and conventional calorie reduction is still lacking, so it has not been established that the effects occur without any change in what or how much you eat.

A walk after a meal does indeed lower the blood sugar peak, and this has been confirmed by multiple randomised studies and meta-analyses. Notably, however, short walking breaks of 2 to 3 minutes spread throughout the day appear to be more effective than a single uninterrupted walk afterwards. The claim implies that a 10-to-15-minute walk is the best approach, but the evidence points more towards frequent short breaks. In addition, little research has been conducted in healthy people with a normal body weight.

Individual studies on fibre supplementation and waist circumference show modest results, but I was unable to find a convincing comprehensive analysis specifically on visceral fat. Visceral fat is also difficult to measure: it requires a scan, and many studies use waist circumference as a proxy, which is not the same thing.

The direction is correct: fiber slows gastric emptying, dampens blood sugar spikes, and promotes satiety. However, it depends strongly on which type of fiber. Randomized studies show that some fibers increase satiety without affecting blood sugar, and vice versa. The threshold of 25 grams is a general dietary guideline, not a measured tipping point above which these effects kick in.

That interval training increases growth hormone release has been genuinely measured; the effect is so reliable that it is even used as a test for growth hormone deficiency. Two caveats, though. Seventy percent of VO2 max is not a high intensity but rather solid endurance work. And the leap from higher growth hormone levels to faster fat burning is greater than it sounds: that peak is short-lived and its contribution to daily fat use is small.

There is research showing this, but in mice. In those studies, white adipose tissue does indeed shift towards brown fat under the influence of fasting, partly via the gut microbiome. In humans, brown fat is far scarcer and harder to measure, and it has not been shown that fasting activates it in us as well.

'Resetting the metabolism' is not something measurable. There is no switch that flips and no default state to return to. What going without food for a full day does do is draw on glycogen stores and increase fat burning, but those effects are gone again the following day.

Correct. Review studies on Ramadan fasting consistently find small decreases in weight, BMI, waist circumference and fat mass. There is, however, an important caveat that usually accompanies this finding: most of these changes have disappeared again within a few weeks after Ramadan.

That the brain can use ketones as fuel is correct and well established. The next step remains an open question: in Alzheimer's disease, small studies using ketones or MCT oil sometimes show a modest improvement, particularly in people without the APOE4 gene, but the studies are small and short-term. As a treatment, this is not substantiated; as a research direction, it is taken seriously.

There are small studies in which people ate somewhat less at the next meal after consuming MCT oil. The effects are modest, have not been found in every study, and were measured over a single day. There is no evidence to support long-term weight loss.

It is established that insulin sensitivity is highest in the morning and declines throughout the day. The explanation via melatonin is plausible and partly supported by evidence, since melatonin suppresses insulin secretion, but it is one of several factors and not the whole explanation.

Correct, and this is better studied than many people think. If you skip breakfast, your body responds to the next meal with a higher blood sugar and insulin spike than it would if you had eaten breakfast. This effect is called the second-meal effect.

In animal studies, fasting demonstrably raises levels of this growth factor in the brain. In humans, this has barely been studied, and the measurements that do exist contradict one another. For a period of twelve hours specifically, there is no evidence whatsoever.

Some studies do observe reductions in inflammatory markers after a period of sunrise-to-sunset fasting. However, many things change at once during that period: eating patterns, sleep, and often body weight as well. Which of these factors is responsible for the effect cannot be determined from this research.

The scales do move faster, but that is largely water rather than fat: without drinking, you can easily lose a kilogram or more of water in a single day, which returns as soon as you drink again. The claim that ketosis is reached more quickly has not been demonstrated. Dry fasting also carries a real risk of dehydration and kidney strain.

This refers to a well-known study in which older adults who did a year of aerobic training ended up with a slightly larger memory centre, by around two percent. That finding is real, but later and larger studies did not consistently replicate the effect on volume. That exercise is good for your brain is well established; growth of the hippocampus is less certain.

This is one of the most exciting research directions at the moment, and the general finding points in the right direction: in large patient databases, diabetic patients taking GLP-1 medications develop dementia less often. However, this is observational research, not a trial, and that is precisely where a key problem arises: those who receive these medications are often better treated and more closely monitored. The randomised trials needed to settle the question are still ongoing, and the first results are expected within a few years.

There is research showing that the relationship between long-term blood sugar levels and cognitive decline extends below the diabetes threshold, without a clear cut-off point. That is a genuine and interesting observation. But precisely for that reason, there is no tipping point at 5.8 percent; that figure suggests a threshold that the research does not support.

Type 2 diabetes demonstrably increases the risk of dementia, but the pooled estimate from review studies puts it at roughly one and a half to two times the baseline risk. A threefold increase is the upper end of what a single study has ever found, and presenting that as the figure makes the risk appear greater than it is. The underlying point still stands: your blood sugar matters for your brain.

Correct: roughly two in three people with Alzheimer's are women. However, the explanation that usually goes with this figure is missing here: women live longer on average, and age is by far the greatest risk factor. Whether something specifically female also plays a role, for instance related to menopause, is being investigated but has not been established.

Abdominal fat in middle age is associated with a higher risk of dementia later in life; this has been found repeatedly in population studies. That said, calling it a strong risk factor is an overstatement: the association is modest and likely runs mostly through blood pressure, glucose metabolism, and inflammation. It is not a standalone cause.

Research shows that muscle loss is indeed a risk with aging, but exercise does genuinely help to counter it. Regular strength training, combined with adequate protein intake, is the best-supported approach to preventing muscle loss, even at an older age. The claim that muscle breakdown accelerates regardless of training efforts is therefore incorrect: training makes a demonstrable difference. Specific evidence on perimenopause as a distinct phase in relation to muscle breakdown is lacking in the available research.

Declining estrogen levels during perimenopause do indeed promote the accumulation of visceral abdominal fat. Observational and mechanistic research shows that hormones and abdominal fat reinforce each other's effects: lower estrogen promotes fat deposits around the abdomen, and that abdominal fat in turn further disrupts metabolism. The relationship is reasonably well supported, although large controlled trials that conclusively prove causality are lacking.

Research clearly confirms that declining oestrogen levels during menopause are associated with greater fat accumulation in the abdominal area (visceral fat) and a worsening body composition. This link is well supported. However, the specific mechanism by which oestrogen suppresses appetite and actively directs fat to subcutaneous tissues, and by which a decline reverses this exactly, goes beyond what available research can establish with certainty: the shift towards abdominal fat is well documented, but the precise role of appetite suppression in this process cannot be firmly established.

Fibre demonstrably contributes to better blood sugar regulation and protects the intestinal wall through short-chain fatty acids, which is consistent with the idea of improved metabolic health. However, a direct link between higher fibre intake and lower body weight is not established in the available research. The effects on gut flora and the immune system also vary considerably from person to person, and large randomised evidence is still lacking for broad health claims.

Research shows that intermittent fasting improves insulin sensitivity in most people and also has positive effects on weight and cardiovascular risk, but the studies are predominantly small and short-term. The claim regarding blood pressure and inflammation goes beyond what the available evidence supports, and for mitochondrial health there is no basis to be found in the available human studies. Furthermore, the specific time window of 15 to 16 hours has not been established as a threshold in the studies that demonstrate positive effects.

The general direction of the claim, that hydrolysed collagen can reduce joint pain, is supported by research, but most of the other details are incorrect. Studies typically use around ten grams per day, not 2.5 grams, and they concern hydrolysed collagen in general, not specifically the chicken variety. The precise figure of 36.9 percent reduction cannot be found in the available evidence. Moreover, that kind of exact number is a sign of false precision: studies do show a positive trend, but outcomes vary from study to study and from population to population.

Research into intermittent fasting shows that fasting can lower inflammatory markers and has a positive effect on metabolic risk factors such as weight, blood pressure and blood sugar, which may indirectly benefit the immune system. However, the specific duration of 16 hours is not firmly supported by evidence, and whether fasting also leads to better clinical immune outcomes, such as fewer infections or remission of immune diseases, has not yet been demonstrated. The general direction is correct as far as inflammatory markers are concerned, but the claim presents more certainty than the evidence provides.

Declining oestrogen levels during and after menopause demonstrably promote the accumulation of abdominal fat, which includes visceral fat around the organs. Observational and mechanistic research supports this link fairly consistently: lower oestrogen impairs insulin sensitivity and promotes fat accumulation around the abdomen, while that abdominal fat in turn further disrupts metabolism. The evidence does, however, rest largely on observational research, so not everything can yet be said about the precise magnitude of the effect.

The evidence that creatine enhances the effects of resistance training is solid: multiple reviews confirm improvements in strength and muscle mass in the context of intensive training. However, the part of the claim stating that creatine increases lean muscle mass without training is not supported by the evidence. The strongest findings apply specifically to the combination with regular resistance training, and the same holds for protein supplementation: training is a necessary condition for maintaining or building muscle mass. The independent effect of creatine on muscle mass outside a training context has not been demonstrated.

The range of 1.2 to 1.6 grams per kilogram per day is well supported for maintaining muscle mass, but the claim goes beyond the evidence on two points. First, this recommendation is based on total body weight, not specifically on target body weight. Second, resistance training is a crucial factor in the underlying research: protein alone is considerably less effective at preventing muscle loss. Furthermore, the word "minimum" implies a hard lower threshold, whereas the studies show an optimal range rather than an absolute cut-off point.

A small pilot study provides preliminary indications that a fasting-mimicking diet may have cell-rejuvenating effects, including the restoration of certain cell types, but whether beta cells in the pancreas actually regenerate in people with type 1 diabetes has not yet been demonstrated in large, well-designed studies. The findings come largely from animal research, and the translation to humans has not yet been sufficiently established. The claim presents as settled fact what is, for now, a promising but unconfirmed hypothesis.

A fasting-mimicking diet improves several health markers, including weight, waist circumference, and inflammatory markers, as small randomised studies show. IGF-1 is typically included as an outcome in that research, but whether it actually decreases cannot be firmly established on the basis of the available evidence. The same applies to systolic blood pressure: the direction appears favourable, but the claim presents the combination of effects more categorically than the studies justify. In addition, several of the researchers involved have financial ties to the commercial product, which calls for caution when interpreting the findings.

Research actually shows the opposite: seed oils such as sunflower oil lower bad cholesterol and are associated with a lower risk of cardiovascular disease, especially compared to saturated fats. The claim that they raise blood pressure or cause disease is not supported by research in humans. The argument that seed oils promote inflammation, a commonly heard justification for this type of claim, also finds no support in the available research.

Creatine combined with resistance training demonstrably improves muscle strength in older adults, and the initial findings in postmenopausal women are promising. However, the claim goes slightly beyond what the evidence supports: for this specific group, large long-term studies are lacking, and the effects on body composition and broader physical performance have not been established firmly enough to speak of a proven combined effect. The direction is right, but the evidence is currently too limited to support the claim in its entirety.

Exercise, including intensive training, demonstrably raises growth hormone and other anabolic hormones in older adults, although the extent varies considerably from person to person. The leap to fat burning and the slowing of ageing goes beyond what the available evidence can firmly support: for those specific chains of effects, there is no conclusive proof in humans, and the only approaches with solid backing in humans remain exercise in general, adequate protein intake and avoiding overeating. The claim therefore contains a kernel of truth, but presents a series of effects as established fact when the research is too limited or too inconsistent to justify that.

Large cohort studies do indeed show that the risk of death drops noticeably as you take more steps each day, and the research supports around 7,000 steps as a beneficial target. However, the specific figure of a 47% lower mortality risk compared to 2,000 steps cannot be firmly established on the basis of the available evidence. Moreover, these are observational associations, not demonstrated cause and effect: more active people may lead healthier lives in a number of other ways, which makes a precise percentage claim vulnerable to criticism.

Eating more fibre is indeed associated with better blood sugar regulation and insulin sensitivity, and a diet high in fibre is one of the best-supported ways to address insulin resistance. However, the threshold of 30 grams is hard to pin down: research points to 25 to 29 grams as a well-supported target, and not every type of fibre works equally well. Moreover, the claim overlooks the fact that other factors, such as physical activity and the rest of one's diet, also play a major role in preventing insulin resistance.

Declining oestrogen levels around menopause do indeed promote the build-up of abdominal fat and increase the risk of insulin resistance. Observational and mechanistic research supports this relationship fairly consistently: hormonal decline and the accumulation of abdominal fat reinforce each other in a cycle, with the abdominal fat in turn further disrupting metabolism. The evidence is largely based on observational research and large controlled trials are lacking, but the general direction of the claim is well supported.

A varied plant-based diet does indeed benefit the gut microbiome, but the evidence for the specific target of 30 different types per week is not well established. What research does show is that a broadly varied diet supports bacterial diversity, although an increased fibre intake only has a measurable effect in people who already have a diverse microbiome. In a controlled study, fermented foods even showed a stronger effect on diversity than a high-fibre diet. The general direction of the claim is correct, but the specific target of 30 is not supported by solid evidence.

Research in animals and small human studies suggests that fasting can activate stem cells and have cell-rejuvenating effects, which supports the general direction of this claim. However, the specific mechanism described, namely that old immune cells are broken down and that stem cells subsequently produce demonstrably healthier new immune cells during refeeding, has not been firmly established in humans through large, well-designed studies. The strongest evidence on the immune effects of fasting concerns reduced inflammatory markers and improved metabolic risk factors, not this precise regenerative process. The claim therefore describes a biologically plausible mechanism, but goes beyond what current evidence in humans supports.

The threshold of 20 grams of protein to preserve autophagy sounds precise, but that level of precision cannot be substantiated. Research shows that no established threshold values exist in humans for activating autophagy, nor for the role of protein intake in that process. Moreover, there is currently no reliable method to measure autophagy in humans, which means that boundaries of this kind cannot be verified in practice. The claim conveys a degree of certainty that the research does not support.

For both the growth hormone peak at 15 hours and the autophagy threshold at 17 hours, no clinically established time standard exists for humans. Research shows that fasting can mechanistically trigger autophagy, but several reviews note that even standard intermittent fasting may be too short to measurably increase autophagy. The precise time thresholds stated in the claim cannot be substantiated on the basis of the available evidence.

Animal studies do indeed show that fasting can stimulate stem cell production and has cell-rejuvenating effects, but in humans the evidence is limited to small pilot studies using biomarkers. The idea of a complete 'reset' of the immune system has not been firmly demonstrated: fasting does lower inflammatory markers and has indirect beneficial effects on the immune system through weight and blood sugar, but hard clinical outcomes such as fewer infections or remission of autoimmune diseases have not been sufficiently studied. The specific claim about 72 hours and its link to stem cell release goes beyond what current research in humans confirms.

The gut microbiome does indeed play a role in oestrogen metabolism, but the relationship works differently from what the claim suggests. Research shows that changes in the gut microbiome after menopause can further suppress already low oestrogen levels, rather than fermented foods making oestrogen more usable for the body's cells. Proven interventions targeting the gut microbiome in menopausal women do not yet exist, and the idea that fermented foods steer oestrogen breakdown in a way that benefits the user is not supported by the available research.

Combinations of strength and endurance training show the strongest results in improving blood sugar regulation in people with type 2 diabetes, and there are multiple indications that such a combined programme also most effectively improves insulin sensitivity. However, the word 'significantly' goes further than the available evidence justifies: how large the reduction in HbA1c actually is, and whether it is always clinically meaningful, depends strongly on a person's weight, diet and baseline situation. For people who are overweight, diet also plays a greater role than the type of training.

Research shows that walking after meals measurably reduces blood sugar spikes, and that effect is well supported by multiple randomised studies and meta-analyses. Whether walking also lowers HbA1c levels cannot be established on the basis of the available research into walking: the findings on HbA1c relate exclusively to medication, not to aerobic exercise. The claim therefore holds for fasting blood sugar and blood sugar response, but the link to HbA1c reduction through walking is not supported by the evidence.

Research shows that soluble fiber lowers blood sugar after a meal, and that the overall composition of the meal plays a role in this. However, the claim that proteins and fiber together specifically prevent a blood sugar crash goes beyond what the available evidence demonstrates. The dampening of the spike is well supported for fiber, but the notion of a 'crash' as a consequence of a spike, and the specific combination with protein, are not confirmed in that way by the research.

Research shows that creatine can promote muscle recovery in older adults (60+) and may have positive effects on memory, particularly in combination with strength training. However, the evidence for a memory effect is strongest for people aged 66 and older, and the findings on muscle recovery are not entirely consistent. For attention specifically, the evidence is less clear: studies show cognitive benefits under conditions of fatigue or sleep deprivation, but not broadly for all older adults. The claim is largely correct, but is somewhat too categorical about both effects simultaneously.

Research does indeed show that more daily steps are associated with a lower risk of death, and that the greatest health benefits occur roughly between 3,500 and 10,000 steps per day. The general direction of the claim is therefore correct. However, the specific figures of a 47% reduction in overall mortality and a 14% reduction in the risk of type 2 diabetes at exactly 7,000 steps compared to 2,000 steps cannot be substantiated on the basis of the available research. Furthermore, these are associations from observational studies, not proven cause and effect.

There are encouraging indications that vitamin K2 may improve bone mineral density in postmenopausal women, particularly in combination with vitamin D. However, the results are not fully consistent and the evidence is not strong enough for a broad recommendation. The claim presents the effect as established, whereas the studies describe it as promising but variable.

Research into hydrolysed collagen peptides (5 g/day) shows positive but limited results for bone density in postmenopausal women. An important caveat is that a considerable share of this evidence comes from industry-funded studies, which limits its reliability. The direction of the claim is correct, but the statement is more definitive than the available research justifies.

Research shows that fasting can reduce inflammation markers and indirectly benefit the immune system, but a true 'reset' of the immune system has not been convincingly demonstrated. No evidence was found for a specific 72-hour fasting period activating stem cells. The claim therefore goes far beyond what the available evidence supports.

A large 2023 American population study found exactly this association: people who ate one meal a day had higher mortality from all causes and from cardiovascular disease. The claim is also carefully worded as an association. One caveat: this is observational research, so a causal relationship has not been established.

This is the wrong way round. Light entering the eyes suppresses melatonin production; an effect that has been measured in a dose-dependent manner, with blue light having the strongest suppressive effect. What is correct is the underlying idea: plenty of daylight during the day synchronises your biological clock, which allows melatonin to kick in at the right time in the evening. But that happens via the clock as an intermediary, not through direct stimulation of melatonin production.

That oestrogen influences the biological clock in the brain is plausible and there are indications to support this, primarily from animal research. How significant that influence is in humans, and whether it explains the sleep complaints seen during the menopause, has not been established.

There is a genuine link between oestrogen and the cholinergic system; this has been described in review articles and in primate research, and it is one of the explanations being seriously investigated. 'Directly linked' is too categorical. Memory complaints during the menopause are also associated with poor sleep, hot flushes and mood, and research has been unable to meaningfully disentangle these factors from one another.

For muscle recovery and muscle soreness after exercise, there is reasonable research suggesting that red light has some effect, though the studies are small and the devices used vary considerably. For joint stiffness, the evidence is thinner. The general direction is not unreasonable, but the claim is stated with too much certainty.

Correct, this is the standard figure in the literature. From around the age of thirty, you lose 3 to 8 percent of muscle mass every ten years, and after sixty that process accelerates. Strength training slows this down considerably but does not stop it entirely.

In people who are not yet training, even ten minutes a day produces measurable gains in strength and fitness. Whether actual muscle mass also increases within twelve weeks is less certain: the studies measuring this are small, and what tends to grow is mainly strength through better muscle coordination, not more muscle tissue.

Correct, and it is one of the simplest interventions available. A few minutes of movement after eating measurably flattens the blood sugar and insulin spike, because the muscles absorb glucose directly.

The enzyme is correct and so is the mechanism: sitting for long periods suppresses lipoprotein lipase activity, and moving activates it again. However, that enzyme works mainly on fats in the blood and on good cholesterol, not on LDL. That last step in the claim is incorrect.

The point at which your body burns the most fat is lower, at around 45 to 65 percent of your maximum effort, and even lower in untrained individuals. At 70 percent you have already passed that point and your body increasingly switches to burning sugar. For anyone training with fat burning as a goal, this advice is therefore off the mark.

Strength exercise produces a peak in growth hormone immediately afterwards, and that is well established. However, this peak is short-lived and turns out not to determine how much muscle you build; that happens through other pathways within the muscle itself. IGF-1, moreover, responds much more slowly and is more strongly linked to your diet.

Short bouts of movement spread throughout the day demonstrably improve your fitness, even if you never get around to a proper workout. That is the strongest part of this advice. For cholesterol, the evidence is much thinner: the effects are small and have not been found consistently.