Broken Metabolism: Why You Feel Cold and Tired All the Time

Many people constantly feel cold, lack energy and immediately blame a “broken metabolism” – but the reality is far more complicated.

Anyone who does not lose weight despite dieting, feels tired all the time and even gets cold in the office while wearing a jumper will often conclude that their metabolism has somehow “gone to sleep”. The phrase is easy to understand and fits neatly into any social-media Reel, but medically it is almost never accurate. Tiredness and feeling cold are usually caused by very different processes within the body.

What metabolism actually means – and why it cannot simply switch off

People often talk about metabolism in everyday life as though it were a switch that can be either on or off. In medical terms, however, metabolism covers every biochemical process that keeps us alive. If it were genuinely “blocked”, we would not remain alive – it is as straightforward as that.

That said, our daily energy balance changes continuously. It is shaped by several factors:

• body composition, including muscle mass and fat mass
• age
• activity habits
• diet and sleep

The largest share comes from the basal metabolic rate. This is the energy the body requires when completely at rest, including for breathing, heartbeat, temperature control and brain activity. It typically accounts for around 60 to 70 per cent of daily energy expenditure.

Other components include:

• Digestion: the energy needed to digest and process food.
• Movement: both planned exercise and unplanned everyday activity, such as climbing stairs, gesturing and standing up.

These spontaneous movements in particular – known technically as NEAT (Non-Exercise Activity Thermogenesis) – are often underestimated. They can distinguish the colleague who seems to “burn calories like a furnace” from the person who feels they gain weight simply by looking at a cake.

Metabolism does not simply collapse – the body gradually adjusts its energy use to our behaviour and body weight.

Why diets can make metabolism seem “sluggish”

The body is highly skilled at survival. It responds very sensitively to prolonged, severe calorie restriction. When energy intake drops dramatically, the body moves into an energy-saving mode.

This happens on several levels:

• Unplanned movement declines without conscious awareness – people sit more and fidget less.
• The body may try to break down muscle mass if protein intake is too low and there is no resistance stimulus.
• Hunger and fullness hormones shift towards “Eat, now!”.

In practical terms, the weight may initially come off quickly. After a few weeks, however, the scales stop moving even though the strict diet continues unchanged. Many people then think: “My metabolism is broken.” In most cases, this is what is actually happening:

• The body has become lighter and objectively needs fewer calories.
• Everyday life becomes more inactive because fatigue leads to less movement.
• Actual calorie intake is underestimated through small snacks, drinks and “tiny bites”.

This is not a defect but a protective response that makes evolutionary sense: the body attempts to preserve fat stores because it assumes there is a famine.

Constantly cold and tired: when illness may be the cause

There are circumstances in which sensitivity to cold and exhaustion can point to a medical issue. A classic example is an underactive thyroid, also known as hypothyroidism.

Common accompanying signs may include:

• persistent tiredness and lack of drive
• feeling very cold, especially in the hands and feet
• dry, rough skin
• brittle hair and hair loss
• slight weight gain or a stubborn increase of a few kilograms

Thyroid problems can slow metabolism slightly, but they are only rarely the real reason for severe obesity.

Weight gain associated with an underactive thyroid is often caused more by fluid retention than by body fat alone. From the outside, this may look like “sudden extra weight”, but medically it is usually not dozens of kilograms.

Age has a much greater effect on energy expenditure. Over time, we gradually lose muscle mass unless we take action to prevent it. This process is called sarcopenia. Muscle tissue is the most important “engine” for calorie expenditure at rest. Less muscle automatically means a lower basal metabolic rate – even if the scales show the same weight.

The hormonal brake caused by crash diets

People who repeatedly follow extreme diets for years eventually notice how difficult weight loss becomes. This is due to an interaction between hormones that respond to weight loss.

When body fat mass falls substantially, several things happen, including:

• Levels of leptin fall. This hormone normally signals: “I am full”.
• Levels of ghrelin rise. It causes hunger and increases appetite.

This is not a pathological disorder; it is part of the body’s protective mechanism. For those affected, though, it can feel brutal: greater hunger, less feeling of fullness, and at the same time less energy and desire to move. In addition, many people lose muscle mass through low-protein diets, which pushes total energy expenditure down even further.

How to optimise your energy expenditure in everyday life

There is no miracle cure that boosts metabolism like a turbocharger. However, there are realistic, scientifically supported approaches that can keep it stable or increase it slightly.

Muscle mass as a natural calorie burner

The most effective way to influence energy use is to retain or build muscle mass. This does not necessarily require a glossy gym; what matters is regular resistance work for the muscles:

• weight training
• bodyweight training, such as press-ups, squats and planks
• strengthening exercises using resistance bands or machines

Every additional kilogram of muscle mass burns more energy at rest than the same kilogram of fat tissue.

Protein: not just for “gym buffs”

Protein is the building material for muscles and tissues. Anyone eating too little protein risks losing more muscle tissue while in a calorie deficit. That lowers energy expenditure – precisely the opposite of what would be helpful during weight loss.

Protein also requires more energy to digest. The body uses noticeably more energy to metabolise protein than it does for fat or carbohydrates. Typical protein-rich foods include:

• low-fat quark, yoghurt and skyr
• eggs
• pulses such as lentils, beans and chickpeas
• fish and lean meat
• tofu and other soya products

Sleep, stress and everyday movement: often overlooked factors

Consistently poor sleep puts a serious strain on the body’s energy balance. Too little sleep:

• reduces insulin sensitivity
• intensifies cravings for sweet and fatty foods
• lowers motivation to be active

Many people report that after bad nights they are more likely to reach for snacks and order fast food rather than cook fresh meals. At the same time, the NEAT contribution falls because tiredness encourages them to move less.

Chronic stress also plays a role. Raised cortisol levels affect appetite and fat storage, especially around the abdomen. Anyone who sleeps little during stressful periods, sits a great deal and snacks as well is giving their body a perfect recipe for weight gain – without their metabolism changing “magically”.

When it makes sense to see a doctor – and what you can do yourself

Anyone who feels extremely tired for months, is very sensitive to cold and notices changes to their skin and hair should have this assessed by a doctor. A simple blood test can establish whether thyroid function, blood sugar, blood count and vitamin levels are normal.

At the same time, it is worthwhile taking an honest look at everyday habits. Useful questions include:

• How many hours each week am I actually active?
• How often do I eat protein-rich foods?
• How often do I sit for more than two hours at a time?
• How many hours do I truly sleep each night?

Many people discover that their metabolism is not “broken”. It is simply responding to too little movement, repeated crash diets, sleep deprivation and increasing muscle loss with age.

Those who address these factors – through some strength training, more conscious protein intake, better sleep and greater everyday movement – often experience two positive effects at once: more energy in daily life and the feeling of no longer being constantly cold. These are usually the clearest signs that the body’s energy balance is becoming better balanced again.