What is ketosis and why does it matter for your wellbeing?

Ketosis is a metabolic state in which the body shifts from using carbohydrates to using fat as its primary source of energy. It’s a completely natural process and familiar to many, especially during fasting or following a ketogenic diet. But how does ketosis occur, what does it feel like, and why do some people find it beneficial – while others feel drained? In this blog, we explore the science and individuality behind ketosis.

The two pathways to ketosis: diet and fasting

There are two distinct ways to enter ketosis: by changing your diet or by adjusting your eating schedule.

A ketogenic diet is high in fat, moderate in protein, and very low in carbohydrates. When daily carbohydrate intake drops below a certain threshold (typically under 50g), the liver begins converting fatty acids into ketones, shifting the body’s energy production toward fat-burning.

Fasting – especially intermittent fasting (like the 16:8 method) or longer breaks between meals – can also lead to ketosis. When blood sugar and insulin levels drop due to not eating, the body starts using stored energy. First, it burns liver glycogen; then it turns to fat.

Both methods can result in ketosis, but the physiological effects may differ depending on the individual and the approach used.

What does ketosis feel like and how does it affect your energy?

In the early stages of ketosis, many people experience mild side effects such as headaches, fatigue, or difficulty concentrating – often referred to as the “keto flu.” These symptoms are signs of the body adapting to a new energy source.

Once adaptation occurs, people often report higher energy levels, improved focus, and more stable blood sugar. This is partly because ketones can provide the brain with a consistent and efficient source of fuel – unlike glucose, which fluctuates with food intake.

However, it’s important to understand that these experiences are highly individual. For some, ketosis brings mental clarity and vitality; for others, it may cause irritability or sleep disturbances.

Genetics help explain why responses differ

One of the most important factors influencing how someone experiences ketosis is their genetics. Your genes affect:

• How efficiently your body can use fat as a source of energy
• How your liver produces ketones
• How well your nervous system and brain tolerate changes in energy supply
• How quickly you recover from shifts in energy intake

Research shows that some people are naturally more efficient fat-burners and adapt to ketosis more easily. Others may struggle to reach or maintain a state of ketosis without experiencing fatigue or other symptoms.

In other words, if a ketogenic diet or intermittent fasting doesn’t feel right for you, it’s not a matter of willpower – it may be rooted in your biology.

What to keep in mind

Whether you approach ketosis through diet or fasting, it’s helpful to remember a few key points:

• Listen to your body. Fatigue, dizziness, or irritability may be signs that your body needs more time to adjust – or that your approach may not be right for you.
• Avoid extreme restrictions. A very low-carb diet isn’t a sustainable solution for everyone. If you aim to enter ketosis through fasting, start gently (e.g., with 12–14 hour eating windows).
• Focus on fat quality. If you’re aiming for ketosis, give your body the best fuel possible. Good fat sources include avocados, olive oil, fatty fish, and nuts.
• Mind your electrolytes. Early ketosis often leads to fluid and mineral loss. Ensure adequate intake of sodium, magnesium, and potassium.
• Honor your individuality. What works for a friend may not work for you. Ketosis is not a goal in itself – it’s just one possible tool to support wellbeing.

In summary

Ketosis is a natural metabolic state in which the body uses fat instead of carbohydrates for energy. It can be achieved either through carbohydrate restriction or fasting. While ketosis can bring balance and vitality to some, it may not be the right fit for everyone – and that’s perfectly okay. Individual differences in metabolism, fat utilization, and energy regulation play a major role in how the body responds to dietary changes.

For one person, a ketogenic diet or intermittent fasting may be a sustainable way to support wellbeing. For another, a completely different dietary structure may be a better fit. That’s why it’s essential to approach your body’s needs based on knowledge, not assumptions.

The Evogenom Eat genetic test offers insight into how your body responds to ketosis and which type of nutrition best supports your individual wellbeing. When your diet aligns with your genetic potential, it becomes easier to make lasting, health-supporting choices – not just short-term experiments.

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