Intermittent fasting has become a popular dietary approach to help people lose or manage their weight. It has also been promoted as a way to reset metabolism, control chronic disease, slow ageing and improve overall health.

Meanwhile, some research suggests intermittent fasting may offer a different way for the brain to access energy and provide protection against neurodegenerative diseases like Alzheimer’s disease.

This is not a new idea – the ancient Greeks believed fasting enhanced thinking. But what does the modern-day evidence say?

First, what is intermittent fasting?

Our diets – including calories consumed, macronutrient composition (the ratios of fats, protein and carbohydrates we eat) and when meals are consumed – are factors in our lifestyle we can change. People do this for cultural reasons, desired weight loss or potential health gains.

Intermittent fasting consists of short periods of calorie (energy) restriction where food intake is limited for 12 to 48 hours (usually 12 to 16 hours per day), followed by periods of normal food intake. The intermittent component means a re-occurrence of the pattern rather than a “one off” fast.

Food deprivation beyond 24 hours typically constitutes starvation. This is distinct from fasting due to its specific and potentially harmful biochemical alterations and nutrient deficiencies if continued for long periods.

4 ways fasting works and how it might affect the brain

The brain accounts for about 20% of the body’s energy consumption.

Here are four ways intermittent fasting can act on the body which could help explain its potential effects on the brain.

1. Ketosis

The goal of many intermittent fasting routines is to flip a “metabolic switch” to go from burning predominately carbohydrates to burning fat. This is called ketosis and typically occurs after 12–16 hours of fasting, when liver and glycogen stores are depleted. Ketones – chemicals produced by this metabolic process – become the preferred energy source for the brain.

Due to this being a slower metabolic process to produce energy and potential for lowering blood sugar levels, ketosis can cause symptoms of hunger, fatigue, nausea, low mood, irritability, constipation, headaches, and brain “fog”.

At the same time, as glucose metabolism in the brain declines with ageing, studies have shown ketones could provide an alternative energy source to preserve brain function and prevent age-related neurodegeneration disorders and cognitive decline.

Consistent with this, increasing ketones through supplementation or diet has been shown to improve cognition in adults with mild cognitive decline and those at risk of Alzheimer’s disease respectively.

2. Circadian syncing

Eating at times that don’t match our body’s natural daily rhythms can disrupt how our organs work. Studies in shift workers have suggested this might also make us more prone to chronic disease.

Time-restricted eating is when you eat your meals within a six to ten-hour window during the day when you’re most active. Time-restricted eating causes changes in expression of genes in tissue and helps the body during rest and activity.

A 2021 study of 883 adults in Italy indicated those who restricted their food intake to ten hours a day were less likely to have cognitive impairment compared to those eating without time restrictions.

3. Mitochondria

Intermittent fasting may provide brain protection through improving mitochondrial function, metabolism and reducing oxidants.

Mitochondria’s main role is to produce energy and they are crucial to brain health. Many age-related diseases are closely related to an energy supply and demand imbalance, likely attributed to mitochondrial dysfunction during ageing.

Rodent studies suggest alternate day fasting or reducing calories by up to 40% might protect or improve brain mitochondrial function. But not all studies support this theory.

4. The gut-brain axis

The gut and the brain communicate with each other via the body’s nervous systems. The brain can influence how the gut feels (think about how you get “butterflies” in your tummy when nervous) and the gut can affect mood, cognition and mental health.

In mice, intermittent fasting has shown promise for improving brain health by increasing survival and formation of neurons (nerve cells) in the hippocampus brain region, which is involved in memory, learning and emotion.

There’s no clear evidence on the effects of intermittent fasting on cognition in healthy adults. However one 2022 study interviewed 411 older adults and found lower meal frequency (less than three meals a day) was associated with reduced evidence of Alzheimer’s disease on brain imaging.

Some research has suggested calorie restriction may have a protective effect against Alzheimer’s disease by reducing oxidative stress and inflammation and promoting vascular health.

When we look at the effects of overall energy restriction (rather than intermittent fasting specifically) the evidence is mixed. Among people with mild cognitive impairment, one study showed cognitive improvement when participants followed a calorie restricted diet for 12 months.

Another study found a 25% calorie restriction was associated with slightly improved working memory in healthy adults. But a recent study, which looked at the impact of calorie restriction on spatial working memory, found no significant effect.

Bottom line

Studies in mice support a role for intermittent fasting in improving brain health and ageing, but few studies in humans exist, and the evidence we have is mixed.

Rapid weight loss associated with calorie restriction and intermittent fasting can lead to nutrient deficiencies, muscle loss, and decreased immune function, particularly in older adults whose nutritional needs may be higher.

Further, prolonged fasting or severe calorie restriction may pose risks such as fatigue, dizziness, and electrolyte imbalances, which could exacerbate existing health conditions.

If you’re considering intermittent fasting, it’s best to seek advice from a health professional such as a dietitian who can provide guidance on structuring fasting periods, meal timing, and nutrient intake. This ensures intermittent fasting is approached in a safe, sustainable way, tailored to individual needs and goals.

Hayley O’Neill, Assistant Professor, Faculty of Health Sciences and Medicine, Bond University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

While many people maintain positive emotional wellbeing as they age, around half of older Australians living in residential aged care have significant levels of depression. Symptoms such as low mood, lack of interest or pleasure in life and difficulty sleeping are common.

Rates of depression in aged care appear to be increasing, and without adequate treatment, symptoms can be enduring and significantly impair older adults’ quality of life.

But only a minority of aged care residents with depression receive services specific to the condition. Less than 3% of Australian aged care residents access Medicare-subsidised mental health services, such as consultations with a psychologist or psychiatrist, each year.

Instead, residents are typically prescribed a medication by their GP to manage their mental health, which they often take for several months or years. A recent study found six in ten Australian aged care residents take antidepressants.

While antidepressant medications may help many people, we lack robust evidence on whether they work for aged care residents with depression. Researchers have described “serious limitations of the current standard of care” in reference to the widespread use of antidepressants to treat frail older people with depression.

Given this, we wanted to find out whether psychological therapies can help manage depression in this group. These treatments address factors contributing to people’s distress and provide them with skills to manage their symptoms and improve their day-to-day lives. But to date researchers, care providers and policy makers haven’t had clear information about their effectiveness for treating depression among older people in residential aged care.

The good news is the evidence we published today suggests psychological therapies may be an effective approach for people living in aged care.

We reviewed the evidence

Our research team searched for randomised controlled trials published over the past 40 years that were designed to test the effectiveness of psychological therapies for depression among aged care residents 65 and over. We identified 19 trials from seven countries, including Australia, involving a total of 873 aged care residents with significant symptoms of depression.

The studies tested several different kinds of psychological therapies, which we classified as cognitive behavioural therapy (CBT), behaviour therapy or reminiscence therapy.

CBT involves teaching practical skills to help people re-frame negative thoughts and beliefs, while behaviour therapy aims to modify behaviour patterns by encouraging people with depression to engage in pleasurable and rewarding activities. Reminiscence therapy supports older people to reflect on positive or shared memories, and helps them find meaning in their life history.

The therapies were delivered by a range of professionals, including psychologists, social workers, occupational therapists and trainee therapists.

In these studies, psychological therapies were compared to a control group where the older people did not receive psychological therapy. In most studies, this was “usual care” – the care typically provided to aged care residents, which may include access to antidepressants, scheduled activities and help with day-to-day tasks.

In some studies psychological therapy was compared to a situation where the older people received extra social contact, such as visits from a volunteer or joining in a discussion group.

What we found

Our results showed psychological therapies may be effective in reducing symptoms of depression for older people in residential aged care, compared with usual care, with effects lasting up to six months. While we didn’t see the same effect beyond six months, only two of the studies in our review followed people for this length of time, so the data was limited.

Our findings suggest these therapies may also improve quality of life and psychological wellbeing.

Psychological therapies mostly included between two and ten sessions, so the interventions were relatively brief. This is positive in terms of the potential feasibility of delivering psychological therapies at scale. The three different therapy types all appeared to be effective, compared to usual care.

However, we found psychological therapy may not be more effective than extra social contact in reducing symptoms of depression. Older people commonly feel bored, lonely and socially isolated in aged care. The activities on offer are often inadequate to meet their needs for stimulation and interest. So identifying ways to increase meaningful engagement day-to-day could improve the mental health and wellbeing of older people in aged care.

Some limitations

Many of the studies we found were of relatively poor quality, because of small sample sizes and potential risk of bias, for example. So we need more high-quality research to increase our confidence in the findings.

Many of the studies we reviewed were also old, and important gaps remain. For example, we are yet to understand the effectiveness of psychological therapies for people from diverse cultural or linguistic backgrounds.

Separately, we need better research to evaluate the effectiveness of antidepressants among aged care residents.

What needs to happen now?

Depression should not be considered a “normal” experience at this (or any other) stage of life, and those experiencing symptoms should have equal access to a range of effective treatments. The royal commission into aged care highlighted that Australians living in aged care don’t receive enough mental health support and called for this issue to be addressed.

While there have been some efforts to provide psychological services in residential aged care, the unmet need remains very high, and much more must be done.

The focus now needs to shift to how to implement psychological therapies in aged care, by increasing the competencies of the aged care workforce, training the next generation of psychologists to work in this setting, and funding these programs in a cost-effective way.

Tanya Davison, Adjunct professor, Health & Ageing Research Group, Swinburne University of Technology and Sunil Bhar, Professor of Clinical Psychology, Swinburne University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.