Kaitlin Day, RMIT University and Sharayah Carter, RMIT University

Intermittent fasting has gained popularity in recent years as a dietary approach with potential health benefits. So you might have been surprised to see headlines last week suggesting the practice could increase a person’s risk of death from heart disease.

The news stories were based on recent research which found a link between time-restricted eating, a form of intermittent fasting, and an increased risk of death from cardiovascular disease, or heart disease.

So what can we make of these findings? And how do they measure up with what else we know about intermittent fasting and heart disease?

The study in question

The research was presented as a scientific poster at an American Heart Association conference last week. The full study hasn’t yet been published in a peer-reviewed journal.

The researchers used data from the National Health and Nutrition Examination Survey (NHANES), a long-running survey that collects information from a large number of people in the United States.

This type of research, known as observational research, involves analysing large groups of people to identify relationships between lifestyle factors and disease. The study covered a 15-year period.

It showed people who ate their meals within an eight-hour window faced a 91% increased risk of dying from heart disease compared to those spreading their meals over 12 to 16 hours. When we look more closely at the data, it suggests 7.5% of those who ate within eight hours died from heart disease during the study, compared to 3.6% of those who ate across 12 to 16 hours.

We don’t know if the authors controlled for other factors that can influence health, such as body weight, medication use or diet quality. It’s likely some of these questions will be answered once the full details of the study are published.

It’s also worth noting that participants may have eaten during a shorter window for a range of reasons – not necessarily because they were intentionally following a time-restricted diet. For example, they may have had a poor appetite due to illness, which could have also influenced the results.

Other research

Although this research may have a number of limitations, its findings aren’t entirely unique. They align with several other published studies using the NHANES data set.

For example, one study showed eating over a longer period of time reduced the risk of death from heart disease by 64% in people with heart failure.

Another study in people with diabetes showed those who ate more frequently had a lower risk of death from heart disease.

A recent study found an overnight fast shorter than ten hours and longer than 14 hours increased the risk dying from of heart disease. This suggests too short a fast could also be a problem.

But I thought intermittent fasting was healthy?

There are conflicting results about intermittent fasting in the scientific literature, partly due to the different types of intermittent fasting.

There’s time restricted eating, which limits eating to a period of time each day, and which the current study looks at. There are also different patterns of fast and feed days, such as the well-known 5:2 diet, where on fast days people generally consume about 25% of their energy needs, while on feed days there is no restriction on food intake.

Despite these different fasting patterns, systematic reviews of randomised controlled trials (RCTs) consistently demonstrate benefits for intermittent fasting in terms of weight loss and heart disease risk factors (for example, blood pressure and cholesterol levels).

RCTs indicate intermittent fasting yields comparable improvements in these areas to other dietary interventions, such as daily moderate energy restriction.

So why do we see such different results?

RCTs directly compare two conditions, such as intermittent fasting versus daily energy restriction, and control for a range of factors that could affect outcomes. So they offer insights into causal relationships we can’t get through observational studies alone.

However, they often focus on specific groups and short-term outcomes. On average, these studies follow participants for around 12 months, leaving long-term effects unknown.

While observational research provides valuable insights into population-level trends over longer periods, it relies on self-reporting and cannot demonstrate cause and effect.

Relying on people to accurately report their own eating habits is tricky, as they may have difficulty remembering what and when they ate. This is a long-standing issue in observational studies and makes relying only on these types of studies to help us understand the relationship between diet and disease challenging.

It’s likely the relationship between eating timing and health is more complex than simply eating more or less regularly. Our bodies are controlled by a group of internal clocks (our circadian rhythm), and when our behaviour doesn’t align with these clocks, such as when we eat at unusual times, our bodies can have trouble managing this.

So, is intermittent fasting safe?

There’s no simple answer to this question. RCTs have shown it appears a safe option for weight loss in the short term.

However, people in the NHANES dataset who eat within a limited period of the day appear to be at higher risk of dying from heart disease. Of course, many other factors could be causing them to eat in this way, and influence the results.

When faced with conflicting data, it’s generally agreed among scientists that RCTs provide a higher level of evidence. There are too many unknowns to accept the conclusions of an epidemiological study like this one without asking questions. Unsurprisingly, it has been subject to criticism.

That said, to gain a better understanding of the long-term safety of intermittent fasting, we need to be able follow up individuals in these RCTs over five or ten years.

In the meantime, if you’re interested in trying intermittent fasting, you should speak to a health professional first.

Kaitlin Day, Lecturer in Human Nutrition, RMIT University and Sharayah Carter, Lecturer Nutrition and Dietetics, RMIT University

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

Eating disorders impact more than 1.1 million people in Australia, representing 4.5% of the population. These disorders include binge eating disorder, bulimia nervosa, and anorexia nervosa.

Meanwhile, more than 4.1 million people (18.9%) are affected by body dissatisfaction, a major risk factor for some types of eating disorders.

But what image comes to mind first when you think of someone with an eating disorder or body image concerns? Is it a teenage girl? If so, you’re definitely not alone. This is often the image we see in popular media.

Eating disorders and body image concerns are most common in teenage girls, but their prevalence in adults, particularly in women, aged in their 30s, 40s and 50s, is actually close behind.

So what might be going on with girls and women in these particular age groups to create this heightened risk?

The 3 ‘P’s

We can consider women’s risk periods for body image issues and eating disorders as the three “P”s: puberty (teenagers), pregnancy (30s) and perimenopause and menopause (40s, 50s).

A recent report from The Butterfly Foundation showed the three highest prevalence groups for body image concerns are teenage girls aged 15–17 (39.9%), women aged 55–64 (35.7%) and women aged 35–44 (32.6%).

We acknowledge there’s a wide age range for when girls and women will go through these phases of life. For example, a small proportion of women will experience premature menopause before 40, and not all women will become pregnant.

Variations in the way eating disorder symptoms are measured across different studies can make it difficult to draw direct comparisons, but here’s a snapshot of what the evidence tells us.

Puberty

In a review of studies looking at children aged six to adolescents aged 18, 30% of girls in this age group reported disordered eating, compared to 17% of boys. Rates of disordered eating were higher as children got older.

Pregnancy

During pregnancy, eating disorder prevalence is estimated at 7.5%. Almost 70% of women are dissatisfied with their body weight and figure in the post-partum period.

Perimenopause

It’s estimated more than 73% of midlife women aged 42–52 are unsatisfied with their body weight. However, only a portion of these women would have been going through the menopause transition at the time of this study.

The prevalence of eating disorders is around 3.5% in women over 40 and 1–2% in men at the same stage.

So what’s going on?

Although we’re not sure of the exact mechanisms underlying eating disorder and body dissatisfaction risk during the three “P”s, it’s likely a combination of factors are at play.

These life stages involve significant reproductive hormonal changes (for example, fluctuations in oestrogen and progesterone) which can lead to increases in appetite or binge eating and changes in body composition. These changes can result in concerns about body weight and shape.

These stages can also represent a major change in identity and self-perception. A girl going through puberty may be concerned about turning into an “adult woman” and changes in attitudes of those around her, such as unwanted sexual attention.

Pregnancy obviously comes with significant body size and shape changes. Pregnant women may also feel their body is no longer their own.

While social pressures to be thin can stop during pregnancy, social expectations arguably return after birth, demanding women “bounce back” to their pre-pregnancy shape and size quickly.

Women going through menopause commonly express concerns about a loss of identity. In combination with changes in body composition and a perception their appearance is departing from youthful beauty ideals, this can intensify body dissatisfaction and increase the risk of eating disorders.

These periods of life can each also be incredibly stressful, both physically and psychologically.

For example, a girl going through puberty may be facing more adult responsibilities and stress at school. A pregnant woman could be taking care of a family while balancing work and other demands. A woman going through menopause could potentially be taking care of multiple generations (teenage children, ageing parents) while navigating the complexities of mid-life.

Research has shown interpersonal problems and stressors can increase the risk of eating disorders.

We need to do better

Unfortunately most of the policy and research attention currently seems to be focused on preventing and treating eating disorders in adolescents rather than adults. There also appears to be a lack of understanding among health professionals about these issues in older women.

In research I (Gemma) led with women who had experienced an eating disorder during menopause, participants expressed frustration with the lack of services that catered to people facing an eating disorder during this life stage. Participants also commonly said health professionals lacked education and training about eating disorders during menopause.

We need to increase awareness among health professionals and the general public about the fact eating disorders and body image concerns can affect women of any age – not just teenage girls. This will hopefully empower more women to seek help without stigma, and enable better support and treatment.

Jaycee Fuller from Bond University contributed to this article.

If this article has raised issues for you, or if you’re concerned about someone you know, call Lifeline on 13 11 14. For concerns around eating disorders or body image visit the Butterfly Foundation website or call the national helpline on 1800 33 4673.

Gemma Sharp, Professor, NHMRC Emerging Leadership Fellow & Senior Clinical Psychologist, The University of Queensland; Amy Burton, Lecturer in Clinical Psychology, University of Technology Sydney, and Megan Lee, Assistant Professor, Psychology, Bond University

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