Constant Tiredness, Feeling Cold and a “Broken Metabolism”

And yet, despite constant tiredness, the scales refuse to move?

Many people blame phases like this on a “broken metabolism”. The phrase makes it sound as though there is a mysterious switch in the body that has simply been set to “off”. The truth is far more matter-of-fact – and more interesting: your metabolism never stops, but it adapts remarkably cleverly to your behaviour, age and body composition.

What lies behind feeling cold and tired all the time

If you often feel chilly, become exhausted quickly and feel as though you have no energy left in the tank, it is easy to suspect a hormonal disorder. Sometimes that is correct, but a combination of lifestyle, diet and expectations of your own body often plays a greater part.

Metabolism does not become “blocked” – it responds. And it responds precisely to what you eat, how you sleep, move and grow older.

In medical terms, metabolism refers to the totality of biochemical processes that keep you alive. If it genuinely stopped, you would no longer be here. What can change, however, is your daily energy expenditure – and this can slow down considerably without you consciously noticing.

How your body uses energy – and where it quietly cuts back

To understand why you feel drained and cold, it helps to look at the elements that make up your energy expenditure.

Component	Share of daily energy expenditure	What it involves
Basal metabolic rate	around 60–70%	Energy for breathing, circulation and organ function while at rest
Dietary thermogenesis	around 10%	Energy your body requires to digest and process food
Movement & NEAT	Remainder	Exercise plus all spontaneous everyday movement, such as walking, gesturing and standing up

One substantial and frequently overlooked element is known as NEAT (Non-Exercise Activity Thermogenesis). It includes every small movement that is not called “exercise”: taking the stairs rather than the lift, fidgeting while on the phone, or walking around your home. This is exactly where the body cuts back first when it senses an energy shortage.

When the body switches into “energy-saving mode”

Longer-term, strict diets can trigger adaptive thermogenesis. Your body registers: “Very little energy is coming in, so a lean period may be ahead.” As a result, you unconsciously move less. You spend more time sitting, walk more slowly and skip small things such as briefly walking over to a colleague.

You will usually not notice these tiny shifts – yet your calorie expenditure still falls. It can then feel as though your metabolism has “gone to sleep”, when in reality it is simply running on low power.

When feeling cold and fatigued may genuinely be medical

Even so, there are circumstances in which being cold and exhausted is more than an adaptation effect. The thyroid is particularly often suspected in these cases.

Warning signs you should take seriously

• persistent, severe fatigue despite getting enough sleep
• noticeably greater sensitivity to cold than other people
• dry, rough skin and brittle hair
• weight gain with no obvious cause

This combination may point to hypothyroidism, meaning an underactive thyroid. It measurably slows metabolism. However, its effect on body weight is smaller than many people assume: it usually involves only a few kilograms, often due to fluid retention (known as myxoedema).

An underactive thyroid rarely explains severe obesity. Diet, physical inactivity and muscle loss play a much greater role in substantial excess weight.

Ageing has a far stronger effect. Over the years, the body loses muscle mass – the technical term is sarcopenia. Muscles are your largest “metabolic engine”. Less muscle automatically means lower energy expenditure at rest. Anyone who continues eating as they did at 25 can quickly end up in a calorie surplus.

Crash diets, hormones and the feeling that “nothing works any more”

Many people who are constantly cold and tired have a history of dieting. In particular, extreme and prolonged calorie-restriction plans leave their mark on hormonal balance.

What happens in the body during radical weight loss

When your body-fat percentage drops substantially, your body adjusts several hormones:

• Leptin falls – this hormone normally signals fullness. Lower leptin levels make you hungrier and less motivated.
• Ghrelin rises – this hormone stimulates appetite. You think about food more often.
• NEAT decreases – you conserve energy by making fewer unconscious movements.

This is not an illness but an ancient protective programme against famine. In a world with a supermarket on every corner, that programme becomes a problem: you are exhausted, feel cold more easily and, at the same time, your body is demanding calories.

If low-protein diets are added to the mix, you lose not only fat but muscle too. That lowers your total energy expenditure even further. You feel weaker, the cold sensation increases – and every subsequent diet becomes harder.

How to get your energy expenditure moving again

The bad news is that there is no miracle cure or pill that can “boost” your metabolism if you continue living as before. The good news is that just a few targeted adjustments can have a measurable effect.

Muscles: your best “metabolism upgrade”

Resistance training – whether using dumbbells, machines or your own body weight – is the most effective way to raise your baseline calorie expenditure. Every additional kilogram of muscle mass uses energy at rest.

• 2–3 strength-training sessions each week not only increase energy expenditure but also improve heat production.
• Strength training is particularly important during weight loss because it protects your muscles from being broken down.
• Greater muscle mass makes everyday movement easier – so you automatically move more.

Anyone who wants to lose weight but avoids strength training is shooting their metabolism in the foot.

Protein: the underestimated source of warmth

Protein has the highest “digestive cost” of all macronutrients. The body burns roughly 20–30% of consumed protein calories simply digesting and metabolising them.

An adequate protein intake:

• preserves muscle during a calorie-restricted phase
• increases fullness and reduces cravings
• incidentally raises energy expenditure through digestion

Good sources include pulses, fish, eggs, dairy products, tofu and lean meat. For many adults, a broad guideline is 1.2–1.6 grams of protein per kilogram of body weight, provided there are no medical reasons against it.

Sleep and body clock: when tiredness becomes a metabolism problem

Chronic sleep deprivation does not directly make you “fat out of nowhere”. However, it shifts several factors in an unfavourable direction:

• Insulin sensitivity declines – the body processes carbohydrates less effectively.
• Hunger and fullness signals become disrupted.
• Cravings for high-fat and high-sugar snacks rise significantly.
• NEAT falls because you are simply too tired to move much.

People who are permanently short of sleep often feel cold more quickly and worn out. In this combination, even the best nutrition plan becomes a theory that is hardly possible to put into practice.

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

If you have felt very cold and extremely tired for months, your skin has changed noticeably and you are gaining weight for no apparent reason, it is worth arranging a check-up with your GP or an endocrinology clinic. Typical laboratory values include TSH, fT3 and fT4, and sometimes thyroid antibodies as well.

At the same time, you can start small experiments in everyday life:

• track your step count consistently for one week and increase it gradually
• add 2–3 simple strength workouts at home
• consciously include protein with every meal
• record your sleep duration and quality

If your energy level changes within two to three weeks, this strongly suggests a functional rather than an organic issue.

Why the “sleeping” phase can be reversed

Many people underestimate just how strongly small daily choices affect the experience of cold and tiredness. Anyone who neglects their muscles for years, drastically cuts calories and consistently sleeps too little at night is unknowingly creating the perfect conditions for a lower metabolism.

The chain reaction is particularly revealing: less muscle mass reduces basal metabolic rate, everyday life becomes more demanding, spontaneous movement declines and you burn even less. At the same time, diets lead to hormonal adaptations that leave you tired and hungry. Sensitivity to cold and exhaustion are therefore warning lights rather than problems in their own right.

With targeted muscle building, sensible protein intake, more everyday movement and sound sleep hygiene, this spiral can often be reversed. The changes frequently feel slower than social-media promises would have us believe, but they work more deeply – and last longer than any new crash diet.