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.

Toddler milk is popular and becoming more so. Just over a third of Australian toddlers drink it. Parents spend hundreds of millions of dollars on it globally. Around the world, toddler milk makes up nearly half of total formula milk sales, with a 200% growth since 2005. Growth is expected to continue.

We’re concerned about the growing popularity of toddler milk – about its nutritional content, cost, how it’s marketed, and about the impact on the health and feeding of young children. Some of us voiced our concerns on the ABC’s 7.30 program recently.

But what’s in toddler milk? How does it compare to cow’s milk? How did it become so popular?

What is toddler milk? Is it healthy?

Toddler milk is marketed as appropriate for children aged one to three years. This ultra-processed food contains:

• skim milk powder (cow, soy or goat)
• vegetable oil
• sugars (including added sugars)
• emulsifiers (to help bind the ingredients and improve the texture)

• added vitamins and minerals.

Toddler milk is usually lower in calcium and protein, and higher in sugar and calories than regular cow’s milk. Depending on the brand, a serve of toddler milk can contain as much sugar as a soft drink.

Even though toddler milks have added vitamins and minerals, these are found in and better absorbed from regular foods and breastmilk. Toddlers do not need the level of nutrients found in these products if they are eating a varied diet.

Global health authorities, including the World Health Organization (WHO), and Australia’s National Health and Medical Research Council, do not recommend toddler milk for healthy toddlers.

Some children with specific metabolic or dietary medical problems might need tailored alternatives to cow’s milk. However, these products generally are not toddler milks and would be a specific product prescribed by a health-care provider.

Toddler milk is also up to four to five times more expensive than regular cow’s milk. “Premium” toddler milk (the same product, with higher levels of vitamins and minerals) is more expensive.

With the cost-of-living crisis, this means families might choose to go without other essentials to afford toddler milk.

How toddler milk was invented

Toddler milk was created so infant formula companies could get around rules preventing them from advertising their infant formula.

When manufacturers claim benefits of their toddler milk, many parents assume these claimed benefits apply to infant formula (known as cross-promotion). In other words, marketing toddler milks also boosts interest in their infant formula.

Manufacturers also create brand loyalty and recognition by making the labels of their toddler milk look similar to their infant formula. For parents who used infant formula, toddler milk is positioned as the next stage in feeding.

How toddler milk became so popular

Toddler milk is heavily marketed. Parents are told toddler milk is healthy and provides extra nutrition. Marketing tells parents it will benefit their child’s growth and development, their brain function and their immune system.

Toddler milk is also presented as a solution to fussy eating, which is common in toddlers.

However, regularly drinking toddler milk could increase the risk of fussiness as it reduces opportunities for toddlers to try new foods. It’s also sweet, needs no chewing, and essentially displaces energy and nutrients that whole foods provide.

Growing concern

The WHO, along with public health academics, has been raising concerns about the marketing of toddler milk for years.

In Australia, moves to curb how toddler milk is promoted have gone nowhere. Toddler milk is in a category of foods that are allowed to be fortified (to have vitamins and minerals added), with no marketing restrictions. The Australian Competition & Consumer Commission also has concerns about the rise of toddler milk marketing. Despite this, there is no change in how it’s regulated.

This is in contrast to voluntary marketing restrictions in Australia for infant formula.

What needs to happen?

There is enough evidence to show the marketing of commercial milk formula, including toddler milk, influences parents and undermines child health.

So governments need to act to protect parents from this marketing, and to put child health over profits.

Public health authorities and advocates, including us, are calling for the restriction of marketing (not selling) of all formula products for infants and toddlers from birth through to age three years.

Ideally, this would be mandatory, government-enforced marketing restrictions as opposed to industry self-regulation in place currently for infant formulas.

We musn’t blame parents

Toddlers are eating more processed foods (including toddler milk) than ever because time-poor parents are seeking a convenient option to ensure their child is getting adequate nutrition.

Formula manufacturers have used this information, and created a demand for an unnecessary product.

Parents want to do the best for their toddlers, but they need to know the marketing behind toddler milks is misleading.

Toddler milk is an unnecessary, unhealthy, expensive product. Toddlers just need whole foods and breastmilk, and/or cow’s milk or a non-dairy, milk alternative.

If parents are worried about their child’s eating, they should see a health-care professional.

Anthea Rhodes, a paediatrician from Royal Children’s Hospital Melbourne and a lecturer at the University of Melbourne, co-authored this article.

Jennifer McCann, Lecturer Nutrition Sciences, Institute for Physical Activity and Nutrition, Deakin University; Karleen Gribble, Adjunct Associate Professor, School of Nursing and Midwifery, Western Sydney University, and Naomi Hull, PhD candidate, University of Sydney

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