Does the time of day you eat affect how quickly you age?
The time at which you eat does appear to matter, although the evidence in humans is still associative. A nightly fasting window of 10 to 12 hours and concentrating your meals during the day are the most concrete guidelines that current research offers.
A nightly fasting window of 10 to 12 hours appears to be a sweet spot for biological aging. In a large American population study with more than 24,000 participants, people with a nightly fasting period of less than 10 hours or longer than 14 hours actually scored worse on biological age markers than the middle group. Cause and effect have not been proven by this, but it is a striking pattern.
Eating out of sync with your biological clock appears to be harmful in any case. Prolonged circadian disruption, such as with shift work or irregular sleep schedules, is strongly associated with higher rates of cardiovascular disease. Controlled laboratory studies show that your internal clock regulates things like blood pressure, blood clotting and metabolism independently of sleep. Eating late, or eating at times that do not align with your day-night rhythm, therefore goes beyond a simple question of calories.
Eating early, only between 8:00 and 14:00, noticeably lowered average blood sugar levels and blood sugar fluctuations in a small study of 11 people. The same group also showed increased activity of genes involved in cell maintenance and stress resistance. That sounds promising, but the study lasted only four days. More robust evidence for reproducibility in larger groups is still lacking.
On the question of meal frequency, the research does not give a clear-cut answer. Six or more meals per day turned out to be riskier than one or two in one prospective study. The large NHANES study, on the other hand, found that people who ate more frequently scored more favorably on biological aging markers. This contradiction has not yet been resolved, and both results are associative. No firm guideline can therefore be drawn from this.
Animal research, including studies in rodents and primates, points fairly consistently to a health benefit from meal timing and intermittent fasting, even without eating less. The translation to humans, however, has barely been explored in large, long-term trials. Most human studies are small or epidemiological in nature, and measure biological aging indirectly through blood markers.
Based on multiple large association studies (including NHANES, n>24,000), reviews, animal research and one small human intervention study (n=11). Causal relationships in humans have not yet been proven through large randomized trials.
Does the order in which you eat food and vegetables during a meal matter?
Eating vegetables and/or protein first and carbohydrates last demonstrably blunts the post-meal blood sugar spike, even in healthy people. It is a small adjustment with no downsides that you can simply try out.
Does eating less help you live longer?
In laboratory animals the effect on lifespan is well established, but in healthy humans direct evidence is lacking. A moderate and sustainable eating pattern is wiser than extreme restriction; discuss major changes to your diet with a dietitian or doctor.
Does it matter for your weight whether your calories come from fat or carbohydrates?
In the long term, the ratio of fat versus carbohydrates matters little for your weight, as long as your total calorie intake stays the same. How well you stick to a diet counts for more than which macronutrients it contains.
Do older adults need more protein than younger people?
Older adults likely need more protein than the standard guideline of 0.8 grams per kilogram suggests. As a healthy older adult, aim for 1.0 to 1.2 grams per kilogram per day, spread well across meals, and combine this with resistance training where possible.
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 without excess weight. If you want to benefit from what has been shown, eating moderately less or following an interrupted eating pattern are the safest, most reasonably supported options.
Do you live longer on a vegetarian or plant-based diet?
A high-quality plant-based diet is associated with less premature death. However, eating strictly vegetarian or vegan has not been proven to be better than a varied diet that occasionally includes meat or fish.