Under eating is more common than you’d imagine, especially in the health/fitness/wellness community. Whilst main stream messages are focused on telling us to eat less, undereating is actually very unhealthy and severely so when it becomes chronic.
Table of contents:
Why under eating is so common
Under eating can be very unintentional. Lack of “time”, planning and being busy are common reasons for undereating. A reliance on hunger/appetite signals is another one – these are not always reliable, can easily be interfered with (stress, mood, exercise, life) and require appropriate interpretation of!
Also a lot of us don’t have a realistic understanding of how much energy is needed to sustain our training and lifestyle, or the amount of energy in different foods. This coupled with main stream messages to “eat less” can result in food choices that simply don’t provide adequate calories to fuel our activity and life.
Why under eating isn’t healthy
If you’re undereating, then you’re likely to have low energy availability. This is different to energy balance (being in an energy deficit), which considers the difference between energy intake from food and energy expended. Energy availability focuses on energy requirements: energy for exercise and energy for health and maintenance.
Being in a negative energy balance and breaking down stores of energy isn’t what the body wants to ideally do or a long-term solution. However, if you are already especially lean/low bodyfat, then you will already certainly be in a state of low energy availability.
If you upset energy availability by reducing energy intake, increasing energy output for exercise, or a mixture of the two, then you have insufficient energy available to support all bodily functions. The body has a priority order of functions, with the top one being to stay alive. Some of the other ones are less essential to immediate health and therefore the body responds and manages by using less energy for these less urgent functions and turning down or off some of its energy costs. This is known as low energy availability.
Low energy availability does not necessarily mean that you have to have especially low bodyfat levels. Although counterintuitive, this is because the body is very good at adapting! Therefore if you have been upsetting your energy availability slightly for a period of time, the body will compensate by turning down its energy costs.
Being in a state of low energy availability increases risk of injury and illness and impairs training, performance and recovery. Longer term, there are severe health complications from it, including reduced sex hormones (females and males), poor bone (osteoperosis) and heart health.
Low energy
This one is kind of obvious since food is the fuel to generate energy required for every single process that takes place in the body. Those online calculators that provide you with your BMR (basal metabolic rate) tell you how many calories that you need to be alive – so lying in bed and not doing anything. Baseline measurements for energy needs for most women are 1800-2200 and men 2000-2400 – but remember that these are baseline and averages for most, not all people. These amounts will definitely be higher for certain people and obviously increase when you train more!
Calorie intake does vary between people and factors such as genes, muscle mass, activity levels etc all influence calorie intake.
Sugar cravings
Sugar is the most easily accessible fuel to generate energy quickly. If you’re low in energy, because you’re not eating enough, then it’s likely that you’ll crave some sugar to fix the issue.
Dependence on caffeine
Similarly to sugar, caffeine can provide that pick me up that will provide that temporary burst of energy to carry you through. If you’ve been undereating, and putting caffeine in the place of food, then it’s understandable and likely that you’ve become more dependent upon caffeine.
Unstable mood / irritable
The brain utilises approximately 20% of energy intake (1). It has lots of different functions to manage and depriving it of sufficient energy it likely to result in mood dips and irritability – which you may feel come from nowhere.
Self-control is one of the first things to go from insufficient energy intake, which might feel like – being unable to focus, manage emotions and cope with stress.
Studies even show that if your blood sugar levels are managed effectively and you get dips, this can be associated with violent and aggressive behaviour (2).
Lack of hunger and/or irregular appetite
Not feeling hungry most of the time, occasionally feeling ravenous and then suddenly getting full and similar, can be signs that you’re not eating enough. Essentially the body doesn’t know if and when it is getting food and this can influence hunger/appetite regulation.
Difficulty losing weight
Whilst starvation mode is a myth, reducing calories and bodyweight aggressively can result in reduced rates of weight loss as the body responds to this. Additionally, if you continually slightly undereat, the body also responds to this.
The way that the body responds is:
Whilst the above apply to losing weight, a reduction in NEAT and TEF also applies to undereating.
Poor digestion
If you’re consuming less then you have less food overall to pass through your digestive system so gut motility slows down. This may mean you are more constipated and do not have the same volume of faeces to pass through you.
Irregular periods / loss of periods
When you miss three or more cycles of periods, it is known as amenorrhea. This can happen for various reasons – stress, pregnancy and certain conditions such as hypothyroidism and PCOS.
It also happens when you are underweight, have low bodyfat levels and can occur when you have low energy availability. However, it doesn’t mean that you have to lose your periods if you have low energy availability.
Feeling cold
Keeping warm requires energy, a process known as thermogenesis. If you’re undereating then you likely have insufficient calorie intake to create heat. This is a process that will be less prioritised by the body.
Additionally, if you’re undereating to the extent that you are underweight, then reduced levels of bodyfat mean that you have less insulation, so you will feel the cold more.
Preoccupation with food
A natural response to undereating is that the brain becomes overly focused with food and think about it more. Also known as brain hunger!
Takeaways:
Under eating is unhealthy!
Be honest about whether you could be under-eating and take action!
You can download my free e-book on how to know if you’re eating enough so you can take appropriate steps!
Do any of the signs resonate with you? Do you think that you could be under eating? Would love to hear in the comments below.
References
Site Credit
© 2023 Antonia Osborne
Antonia,
MSc, RNutr
Performance Coach
Registered Sports & Exercise Nutritionist
