Metabolism
Blood sugar, insulin and weight , the engine of aging.
114 answers, from 752 studies
Last updated: July 2026
Key questions
How much berberine do you need per day?
The best-supported doses range between 0.6 and 1 gram per day, depending on your goal. If you use metformin, discuss berberine…
Moderate evidence
What do we really know about metformin and ageing?
Metformin may extend healthy years by helping to prevent disease, but whether it also slows ageing itself in healthy people…
Preliminary evidence
What does stable blood sugar do for healthy ageing?
A stable, low blood sugar is associated worldwide with more healthy life years. The association is clear, but the exact gain…
Yes · Moderate evidence
Do your hormones influence how quickly you age?
Hormones do influence ageing, but do not control it entirely. Fat distribution, muscle mass and inflammatory processes are all…
Yes · Moderate evidence
Does black seed oil work as a supplement?
For people with type 2 diabetes, there is reasonably consistent evidence that black seed oil lowers blood sugar, cholesterol,…
Moderate evidence
Does a NAD infusion (IV drip) make sense?
There is no clinical evidence that a NAD infusion does anything for your health or ageing. Oral NAD supplements do…
Preliminary evidence
Does the fasting-mimicking diet, such as Prolon, actually work?
The fasting-mimicking diet shows real effects on weight, fat mass and blood pressure in small randomised studies, but almost…
Yes · Moderate evidence
What works better to raise NAD+: NMN or NR?
NMN and NR raise blood NAD+ equally well, but there is an important legal difference: NR is authorised as a supplement in the…
Preliminary evidence
Which form of iron is best absorbed?
Haem iron from meat, fish and poultry is clearly better absorbed than the form of iron from plant-based foods. If you eat…
Strong evidence
What is the relationship between fatty liver and type 2 diabetes?
Fatty liver and type 2 diabetes mutually reinforce each other, with abdominal fat and insulin resistance at their shared core.…
Does excess weight really make your hormones worse?
Excess weight disrupts multiple hormones simultaneously, with insulin resistance being the most strongly supported. If you…
Does chewing slowly really help with better digestion?
There is no direct evidence that chewing more slowly improves digestion in healthy people. The association between poor…
Insufficient evidence
How does your body fat affect hormone production as you get older?
Body fat has a considerable influence on your hormonal balance as you age: more abdominal fat disrupts insulin sensitivity,…
What does caffeine do to your stress hormones when you drink a lot of it?
High caffeine intake raises your cortisol, especially during stress or exercise and later in the day; you partially adapt to…
Does the order in which you eat your food affect your digestion?
The available studies do not answer this question, so no conclusion can be drawn from them. If you want to learn more about…
Insufficient evidence
What is the role of bile acids in healthy digestion?
Bile acids are indispensable for fat digestion, the absorption of vitamins A, D, E, and K, and a healthy cholesterol balance.…
Can low blood sugar disrupt your hormones, and how do you notice it?
Low blood sugar immediately raises stress hormones and causes symptoms such as trembling, sweating and irritability. People…
Yes · Moderate evidence
Are the gut bacteria of lean people different from those of heavier people?
The gut bacteria of people with excess weight differ measurably from those of lean people, but whether those bacteria are the…
What does a high-fat diet do to your gut microbiome?
A high-fat diet noticeably disrupts the gut microbiome: less bacterial diversity, more harmful species and a leaky gut wall…
Does having type 2 diabetes increase your risk of certain cancers?
Type 2 diabetes increases the risk of at least six cancer types, most likely primarily through chronically elevated insulin…
Does drinking apple cider vinegar help your digestion?
There is no research whatsoever showing that apple cider vinegar improves digestion. If you want to use apple cider vinegar…
No · Preliminary evidence
What happens to your cells when you don't move enough?
Moving too little demonstrably disrupts how your cells handle sugar, signals and inflammatory processes. Even a small increase…
Can your gut microbiome control your appetite and hunger?
Your gut microbiome influences your appetite through hormones, nerve signals and substances produced from fibre fermentation.…
Does diabetes increase the risk of bone fractures?
Diabetes clearly and demonstrably increases the risk of bone fractures, even when bone density appears normal. If you have…
What does eating too much sugar do to your gut health?
Eating a lot of sugar probably disrupts your gut microbiome and makes the gut wall more permeable, but it is the combination…
What is sleep debt and can you really pay it back?
Sleep debt is real and has measurable effects on your cognitive function and metabolism, but full recovery takes more than a…
Yes · Moderate evidence
Does someone with diabetes age faster biologically?
Yes, diabetes noticeably accelerates biological ageing: the risk of cardiovascular disease, dementia, and premature death…
Does the timing of meals throughout the day affect your weight?
When you eat matters: meals earlier in the day appear more favourable for your metabolism than eating late, although the…
Yes · Moderate evidence
What does pregnancy do to your hormonal balance in the long term?
Pregnancy demonstrably has long-term effects on your metabolism and hormonal balance, but most effects are well documented for…
Does eating more fibre help against high blood sugar?
Eating more water-soluble fibre probably helps in lowering high blood sugar, but the overall meal composition also plays a…
Yes · Moderate evidence
What does alcohol do to your blood sugar and insulin sensitivity?
The effect of alcohol on your blood sugar depends strongly on when you drink, how much, and what you eat alongside it. On an…
Does cinnamon really lower your blood sugar?
Cinnamon can modestly lower fasting blood sugar in type 2 diabetes, but whether that makes any meaningful difference to…
Moderate evidence
Does fasting (intermittent fasting) help improve your insulin levels and other hormones?
Fasting probably improves your insulin levels, but most studies are small and short-term. Eating early in the day appears to…
Yes · Moderate evidence
Does it matter for your weight whether your calories come from fat or carbohydrates?
For long-term weight loss, the ratio of fat to carbohydrates makes little difference as long as your total calorie intake…
No · Moderate evidence
Does strength training work better against high blood sugar than cardio?
Strength training appears to work better than cardio alone in people with diabetes and a normal weight, but in overweight…
Moderate evidence
Does being overweight affect your bone density?
Being overweight does not straightforwardly increase bone density, and the location and amount of fat strongly determine…
What does chronic stress do to your weight in the long run?
Chronic stress contributes to long-term weight gain and abdominal fat through elevated cortisol, inflammation, and less…
How bad is sitting for too long for your blood sugar and metabolism?
Sitting for long uninterrupted periods noticeably impairs your blood sugar and metabolism, but short breaks of 2-3 minutes of…
What is glycation and how does sugar damage your cells from the inside?
Sugar damages your cells through a chain of chemical reactions that affect proteins, power plants, and small blood vessels.…
Does type 2 diabetes increase your risk of dementia?
Type 2 diabetes substantially increases the risk of dementia, and the younger you are at diagnosis, the greater that risk.…
What is the difference between high blood sugar and a blood sugar spike?
Chronically high blood sugar and a blood sugar spike are two different things that each require their own approach. If your…
What does alcohol do to your hormones when you drink it regularly?
Regular and excessive drinking lowers testosterone, disrupts your sleep hormone, and damages the liver. If you want to know…
Does cold showering or an ice bath speed up your metabolism?
Cold water raises your metabolism only during the immersion itself; after that the effect disappears. If you want to build…
No · Preliminary evidence
What does excess weight do to your inflammation levels?
Excess weight structurally raises your inflammation levels through multiple biological pathways. Exercise, and strength…
What does intermittent fasting do to your insulin sensitivity?
Intermittent fasting improves insulin sensitivity, but the studies are still mostly small and short-term. If you want to try…
Can too much sugar weaken your immune system?
Chronically high blood sugar, as seen in diabetes and obesity, demonstrably weakens the immune system, but whether a few…
Preliminary evidence
Can poor sleep cause me to develop diabetes sooner?
Consistently sleeping too little or poorly demonstrably increases your risk of type 2 diabetes, so it is worthwhile taking…
Yes · Moderate evidence
What does excess weight do to your brain in the long run?
Excess weight harms your brain in multiple ways at once: less brain tissue, weaker connections and a higher risk of dementia.…
Does muscle tissue burn more calories than fat, even at rest?
Muscle tissue burns more calories at rest than fat tissue, and strength training produces a measurable increase in resting…
What is visceral fat and why is it more dangerous than subcutaneous fat?
Visceral fat is more dangerous than subcutaneous fat because it acts directly on the liver, releases more inflammatory…
Does it matter in what order you eat your food and vegetables during a meal?
What you eat before or early in your meal can noticeably influence your blood sugar response. The most concrete takeaway:…
Yes · Preliminary evidence
Does magnesium help with insulin resistance?
There is a reasonable amount of evidence that magnesium has a beneficial effect on insulin resistance, particularly if your…
Yes · Moderate evidence
Why do you gain weight more easily after 40, even if you eat the same amount?
After forty, your body burns fewer calories, mainly due to muscle loss and a lower resting metabolism. You therefore do not…
Does a large belly increase my risk of cancer more than being simply overweight?
A large belly raises the risk of colorectal cancer in particular more than ordinary overweight does, and measuring your waist…
Yes · Moderate evidence
Is brown fat really different from regular fat, and can I activate it?
Brown fat is genuinely different from regular fat and you can activate it, with cold exposure having the strongest evidence.…
Yes · Strong evidence
What does chronically high cortisol do to your belly fat and blood sugar?
Chronically high cortisol directs fat toward the abdominal cavity and increases the risk of insulin resistance and type 2…
How does metformin work in the body?
Metformin lowers blood sugar primarily by inhibiting glucose production in the liver and through effects on the gut, but…
Does metformin help with weight loss?
Metformin helps with weight loss, but the effect is modest: expect a few kilograms, not a dramatic transformation. Lifestyle…
Yes · Moderate evidence
Can you take metformin without having diabetes?
There is limited evidence that metformin can reduce weight in people without diabetes, but the risks, including possible heart…
Preliminary evidence
Does strength training help against insulin resistance?
Strength training probably helps against insulin resistance, although the effect is most strongly demonstrated in combination…
Yes · Strong evidence
How do you measure insulin resistance?
There are several ways to measure insulin resistance, ranging from an accurate but expensive hospital method to simple blood…
Does insulin resistance accelerate ageing?
Insulin resistance is associated with measurably faster biological ageing, greater muscle loss, and possibly a higher risk of…
Yes · Moderate evidence
What foods improve your insulin sensitivity?
Diet can clearly improve your insulin sensitivity: a wholesome diet high in fibre, eating your largest meal early in the day,…
Moderate evidence
What are the earliest signs of insulin resistance?
Early signs of insulin resistance are measurable long before a diabetes diagnosis: elevated fasting insulin, abdominal fat,…
Can your HbA1c also be too low?
An HbA1c below 5.0% is associated with an increased risk of death in people without diabetes, although this is likely a signal…
Yes · Moderate evidence
How often should you have your HbA1c measured?
The ideal measurement frequency differs by situation: with prediabetes, annual monitoring is worthwhile; with type 2 diabetes,…
Moderate evidence
What does your HbA1c tell you about your risk of diabetes and ageing?
An elevated HbA1c, even well below the official diabetes threshold, is associated with a greater risk of diabetes, kidney…
How do you lower a high HbA1c?
Several medications demonstrably lower HbA1c: the weekly semaglutide injection has the strongest evidence base, but oral…
Strong evidence
What is a healthy HbA1c value?
There is no fixed 'healthy' HbA1c value: lower within the normal range appears to be better, but how low is optimal also…
Do proteins inhibit or boost your autophagy?
Eating a lot of protein, especially red and processed meat, likely inhibits autophagy via higher IGF-1 levels. If you want to…
Yes · Moderate evidence
How many hours of fasting are needed to activate autophagy?
There is no proven hourly threshold for activating autophagy in humans. If you use this as a reason for a fasting pattern, be…
At what age does taking NAD+ supplements make sense?
There is no established age at which NAD+ supplementation becomes worthwhile; studies focus on middle-aged and older adults,…
Preliminary evidence
How does too much LDL or ApoB lead to clogged arteries?
Too many LDL particles and too much apoB in your blood set off a chain reaction that slowly clogs arteries. The evidence for…
What is the relation between NAD+ and vitamin B3?
Vitamin B3 is the only dietary building block for NAD+ in your body -- that relationship is causal and well supported. Whether…
What is the controversy with NAD+?
NAD+ supplements demonstrably raise your NAD+ levels, but whether that actually does anything for your health has not yet been…
Does NAD+ cause weight gain?
There is no scientific evidence that NAD+ supplements such as NMN or NR cause weight gain. Animal research even suggests the…
No · Preliminary evidence
What are the effects if you take NAD every day?
Taking 600-900 mg of a NAD supplement per day raises your NAD levels and provides some benefit for endurance, but long-term…
Does coffee activate mTOR?
Caffeine does not activate mTOR -- it actually inhibits it. Whether this also holds for normal coffee consumption in humans…
Chronic sleep deprivation: how harmful is it for weight and hormones?
Chronic sleep deprivation disrupts your hormones and metabolism after just a few nights. Structurally sleeping too little…
What is AMPK and how do you activate it (through fasting or exercise)?
Exercise is the most solid way to activate AMPK. Fasting has surprisingly little measurable effect in muscle itself, and a…
Yes · Moderate evidence
What does insulin do to the ageing process?
Chronically high insulin signalling contributes to accelerated ageing and age-related diseases; maintaining your insulin…
Is yo-yo dieting -- repeatedly gaining and losing weight -- bad for me?
Yo-yo dieting has real biological disadvantages, such as a lower metabolism and fatty tissue that appears to become more…
Moderate evidence
Does eating a lot of sugar give you type 2 diabetes?
Sugary drinks clearly and demonstrably increase your risk of type 2 diabetes. Sugar from solid food barely does. The biggest…
Does it make sense to limit blood sugar spikes, even without diabetes?
Limiting blood sugar spikes makes sense even without diabetes. The simplest and best-supported method is to take a short walk…
Yes · Preliminary evidence
Why is it harder for me to lose weight than it used to be?
Ageing lowers your energy expenditure through muscle loss and a slower metabolism, making weight loss objectively harder.…
Does my metabolism really slow down as I get older?
Your resting metabolism really does decline with age, but the biggest culprit is muscle loss, not some mysterious metabolic…
Does it matter what time of day I eat?
Eating earlier in the day is more beneficial for your weight, blood sugar and hormonal balance than eating late or at night.…
Yes · Moderate evidence
Are smoothies and fresh juice just as healthy as whole fruit?
Whole fruit beats fruit juice: more fibre, greater satiety and fewer free sugars. Smoothies fall somewhere in between, but are…
No · Moderate evidence
Does the combination of glycine and NAC (GlyNAC) help against aging?
GlyNAC shows promising results in a small human study on oxidative stress, muscle function and inflammation, but the evidence…
Preliminary evidence
Does urolithin A from pomegranate do anything for your muscles and energy?
UA supplements (1000 mg/day) improve muscular endurance in older adults, but do not demonstrably increase total energy…
Moderate evidence
Does my weight and metabolism change during menopause?
During menopause, the rate of fat gain doubles and you lose muscle mass, even if the scales do not show it. The fat shifts…
Does losing weight noticeably improve my blood pressure and cholesterol?
Losing weight noticeably lowers your blood pressure and improves your cholesterol profile, but which value improves the most…
Yes · Strong evidence
Which works better for weight loss: semaglutide or tirzepatide?
Tirzepatide produces greater weight loss and better blood sugar control than semaglutide on average. Gastrointestinal…
Yes · Moderate evidence
Is my gut flora linked to being overweight?
Your gut microbiome is probably linked to excess weight through multiple mechanisms, but a proven causal relationship in…
Do you actually live longer if you structurally eat fewer calories?
In laboratory animals, eating less convincingly extends lifespan, but this has not yet been demonstrated for healthy people…
Moderate evidence
Does being overweight increase my risk of cancer, and if so, which types?
Excess weight increases your risk of at least 13 types of cancer, including uterine, colorectal, breast and liver cancer.…
What is a healthy HDL (good cholesterol) level, and can I raise it?
Raising HDL through lifestyle is possible, but your genes set the ceiling. Lowering triglycerides through less sugar and…
Moderate evidence
What is a healthy waist circumference and why does it matter?
A larger waist circumference is associated with a greater risk of diabetes, bone fractures, gum disease and premature death.…
What do artificial sweeteners do to your gut microbiome?
Whether artificial sweeteners truly disrupt your gut microbiome is not yet clear: studies contradict one another. Until there…
What is NAD+ and what does it do in your body?
NAD+ is an indispensable molecule for energy, DNA repair and cell health, but the question of whether you should actively…
Does berberine help against high blood sugar (the natural metformin)?
Be careful with this. Berberine measurably lowers blood sugar, but EFSA could not establish a safe intake level (signs of DNA…
Yes · Moderate evidence
How bad is fructose compared to regular sugar?
Fructose places a greater burden on the liver than glucose and raises triglycerides, belly fat and uric acid more. But regular…
How do I know whether my blood sugar is healthy (prediabetes)?
Prediabetes is detected through a simple blood test at your GP's practice. For most people it is not an inevitable step toward…
How much sugar is too much?
Getting more than 10% of your daily calories from free sugars, roughly 50 grams, increases the risk of metabolic syndrome,…
I am overweight -- what will losing weight do for me?
Losing weight when overweight or obese produces real health gains. Combine a healthy diet with aerobic training and strength…
Does excess weight accelerate ageing?
Excess weight demonstrably accelerates biological ageing, but metabolic health counts at least as heavily as the number on the…
What is NAD+ and why does it decline as you age?
NAD+ is an indispensable energy carrier and guardian of your DNA, and your body produces less of it as you age. The mechanisms…
What does your thyroid gland do to your metabolism and energy?
A properly functioning thyroid directly determines your energy expenditure, weight and cholesterol. If you suffer from…
Do diabetes pills (SGLT2 inhibitors) also work against ageing?
For people with heart or kidney problems, large trials show that SGLT2 inhibitors clearly do more than lower blood sugar…
Moderate evidence
Does a walk after eating help with your blood sugar?
A short walk after eating, or better still several short walking breaks of 2 to 3 minutes spread throughout the day, is a…
Yes · Strong evidence
Does coffee help prevent type 2 diabetes?
Three to four cups of coffee a day is associated with a lower risk of type 2 diabetes, but this is an observed association,…
Yes · Moderate evidence
What is metabolic syndrome and how do I get rid of it?
Metabolic syndrome is silent but serious: years without symptoms, yet with a substantially elevated risk of cardiovascular…
Yes · Strong evidence
Is a glucose meter useful if you don't have diabetes?
Without diabetes, a glucose monitor gives you some genuinely interesting information about how your body responds to food,…
Preliminary evidence
What is insulin resistance and can I reverse it?
For most people, insulin resistance can be substantially reduced or even reversed through more exercise and a healthier diet,…
Yes · Strong evidence
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