5 signs you're not eating enough

Amy Wood - Nutritionist | 24 Apr, 2024

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We know that to lose weight, we need to place our bodies in a calorie deficit. This is most often achieved by eating less, but it's possible to take this too far. Here are 5 telltale signs you're under-fuelling your body, that just might be the roadblock to your weight loss success.


1. You are constantly hungry

The first major sign that your calorie deficit is too severe is a persistent feeling of hunger. It might seem obvious, right? Leptin is one of the hormones that makes us feel full. When our calorie intake drops too low, concentrations of leptin decrease. At the same time, the hormone that tells us we’re hungry (called ghrelin) increases. This is often what leads to the cycle all too common with people trying to lose weight – restricting too much throughout the week, and then throwing in the towel and bingeing at the weekends.

Low energy

2. Your energy levels are at an all-time low

Another telling sign you aren’t eating enough is low energy levels. Calories are the units of energy that the body uses to function. In a mild deficit, our body can use its storage of fat over time to meet its energy needs, but if we aren’t fuelling it sufficiently through our diets to perform even basic functions, we can’t expect it to work at normal capacity. So if you find yourself nodding off at your desk, exhausted by the end of every day, or even feeling faint, especially after physical activity, it could be a warning that your calorie deficit is too drastic.


3. You are irritable and snappy

You’ve probably heard the term ‘hanger’ – used to describe the seemingly irrational irritation we can feel before our morning coffee and a bite to eat. But there is actually science behind this response! Cortisol and adrenaline are hormones associated with anger and anxiety stress responses due to their role in the ‘fight-or-flight’ mechanism. These two hormones are triggered by low blood sugar levels, so the less we eat, the more likely we are to fire off the fight-or-flight centres of our brain, leading to feelings of stress, anger and anxiety.

As circulating levels of adrenaline are higher, undereating has also been associated with sleep problems, which can perpetuate feelings of anxiety and the dreaded ‘hanger’.


4. You are constipated

If you aren’t putting as much food into your body, you’ll probably experience less coming out of your body. It’s a less-than-pleasant topic, but constipation can be extremely uncomfortable and shouldn’t go untreated. You’re also less likely to be eating enough fibre, which could contribute to a blocked up digestive system. You may also be consuming less water through both food and drink, which normally helps to keep everything moving too.

Remember, 30g a day is the daily fibre target. It can be quite a challenge for most people, even when not on a calorie-reduced diet.

Stalling weight loss

5. Your weight loss is stalling

Eating less can make weight loss harder?! It might seem counter-intuitive, but it’s true. Eating too little can affect your metabolic rate long term and is likely to make maintaining lean tissue harder, so while you might initially see a lower number on the scale, this will represent both fat loss and muscle loss. As muscle tissue uses more calories day to day than fat, people with more lean tissue will have a higher metabolic rate. Higher metabolic rate equals more calories burned. So, losing muscle tissue isn’t ideal when losing weight, as your metabolic rate will decrease, making further weight loss harder.

Severely slashing your calorie intake for a prolonged period might also stimulate your body to actively decrease your metabolic rate in an attempt to conserve energy. The scientific name for this is adaptive thermogenesis but is also referred to as metabolic slowdown. Research is ongoing to improve our understanding of the mechanisms that trigger and promote metabolic slowdown, but all we know for now is that overdoing your calorie deficit might be more of a hindrance than a help when it comes to weight loss.

So what should I do if I identify with one or more of these signs?

If you've cut your calories for a short time (a matter of weeks) and have noticed you are experiencing some of these side effects, don't worry! Returning your calorie intake back to a safe level should get your body firing on all cylinders again fairly quickly. However, if you’ve been undereating for several months, you might be a little more apprehensive to up your intake. This is completely understandable, as there's a chance that suddenly increasing your energy intake at this point could cause a temporary weight gain blip.

To avoid this, a gradual approach is the best course of action – sometimes referred to as 'reverse dieting'. Although research into this method is still emerging, the current body of evidence generally suggests a positive effect. Start by adding 50-100 calories onto your current intake and aim to hit that for 3-4 weeks. Then, steadily increase by 50-100 calories every couple of weeks. Not only will this method give your metabolism time to adjust, but it will also be more manageable if you've become accustomed to eating less food for a while.

The best foods to boost your energy and nutrient intake

When looking for foods to boost your energy intake and help reach your calorie target, you should opt for snacks that are both calorie dense and nutrient dense. Nuts are an excellent choice. They are a good source of unsaturated fats, which promote heart health. They also contain protein and fibre, two of the best nutrients to help you feel fuller for longer. Depending on the variety of nut you choose, you'll also get different levels of vitamins and minerals – vitamin E, folate, magnesium, zinc, selenium and potassium to name just a few.

Other foods that provide healthy calories are avocados, olives and oily fish – all are high in fat, but the good unsaturated kind. If you're currently choosing 'light' and 'diet' versions of foods like yogurt and cereal bars, try swapping a few for regular versions throughout the week. The 'low fat', 'low calorie' versions tend to be higher in added sugar, so you might find your sugar intake for the week also goes down – an added bonus!

Nutritionist Amy Wood (ANutr), MSci BSc Nutrition has a keen interest in the relationship between diet and health. Having been published in the European Journal of Nutrition, Amy is passionate about making evidence-based nutrition accessible to everyone and helping others to adopt a food-focused approach to taking control of their health.

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