Does fasting or eating less help your memory and concentration?
Eating less or intermittent fasting probably shows a small positive effect on memory and concentration. The evidence is there, and the effect is clearest in people who already have mild memory problems.
Eleven randomised studies combined show that dietary restriction, both calorie restriction and intermittent fasting, has a small but measurable positive effect on memory and general cognitive functioning. The effect is modest. In people with mild memory problems the effect is somewhat larger than in people with a healthy memory.
Which form of fasting yields the most benefit is not yet clear. A DASH diet or low-glycaemic diet appears to offer cognitive advantages. A small study in older people with insulin resistance found that 5:2 fasting (two days per week of severely restricted eating) improved memory and concentration, and also reduced signs of brain ageing on a brain scan. A healthy eating pattern without a fasting schedule also helped in that same study, but on some measures slightly less so. The study was too small to make broad claims.
Short-term fasting, such as going without food for a day, gives a mixed picture. Some studies see no effect at all on concentration or reaction speed, while others find small deficits in executive functions. The same applies to young people who fast during Ramadan: the studies are too small and too varied to say whether memory improves or deteriorates as a result.
The theory that fasting protects the brain via a restorative substance that supports learning and memory (BDNF) is not yet supported by the evidence. Of sixteen studies, five found an increase in that substance, five found a decrease, and six found no change. Claims that fasting protects the brain through this mechanism have not yet been proven in humans. Animal research into Alzheimer's disease does show that calorie restriction produces the most consistently positive outcomes, but whether this also applies to humans has not yet been demonstrated.
In people with cardiovascular disease, one study actually found a negative effect on problem-solving ability with calorie restriction. If you have a heart condition and are considering a fasting schedule, discuss this with your doctor first.
The answer rests on several summaries of randomised studies and one separate small randomised study. The most solid finding comes from eleven summarised randomised studies (a positive but modest effect). The researchers in the broader reviews generally rate the available studies as low quality: few participants, short duration, varying fasting methods and cognitive tests. The BDNF evidence is based on sixteen studies with entirely contradictory outcomes. Animal research into Alzheimer's disease is not directly translatable to humans.
What does a higher body temperature do to your concentration and memory?
A higher body temperature worsens your working memory and attention, and makes you more impulsive without making you more accurate. Staying cool, especially during mentally demanding tasks, protects your thinking ability.
Does creatine also help with memory and concentration?
Creatine can improve your memory, but mainly if you are older, vegetarian, or your brain is under pressure. If you are a young, healthy meat eater who sleeps well, the effect is small to negligible.
What does your estrogen level do to your memory and concentration?
Oestrogen has a measurable influence on memory and concentration, and the decline during perimenopause is accompanied by temporary cognitive complaints in many women. Whether hormone therapy reverses this depends on timing and individual circumstances; discuss this with your doctor if it is affecting you.
How do you train your memory effectively?
Memory can be trained, but the smartest investment is regular exercise: that has the strongest and broadest support for cognition and memory. Targeted memory training helps, but less spectacularly than is often assumed.
Does a fasting-mimicking diet work better than simply eating less?
Research suggests that a fasting-mimicking diet has a greater effect than the same calorie deficit without a fasting pattern. Bear in mind that almost all studies have ties to the commercial manufacturer.
Does varying the timing of your fasting window help reduce feelings of hunger?
Intense exercise and structured fasting help against uncontrolled hunger. The timing of your fasting window matters less than the way you fast or exercise.