Your Body Was Built to Use More Than One Fuel.
Glucose, fat and ketones are part of an interconnected energy system. Understanding how your body moves between them can reveal a richer picture of your metabolic health.
SugaTone helps you connect the numbers with the behaviours and circumstances behind them.
Carbohydrate route
- Food
- Glucose
- Cellular energy
Fat route
- Stored fat
- Fatty acids
- Liver
- Ketones
- Cellular energy
Simplified educational illustration of energy pathways. Real metabolism involves many additional steps and overlapping processes.
Section 01
Your Glucose Reading Has a Story Behind It.
Person A
5.5 mmol/L
- Recently ate
- Poor sleep
- Low activity
- Low ketones
Person B
5.5 mmol/L
- Fasted overnight
- Exercised
- Different ketone level
- Different meal history
The glucose number may be identical, but the surrounding metabolic context can be very different. This is why SugaTone brings multiple signals together.
Illustrative example — not medical guidance.
Your metabolic story
- Glucose
- Ketones
- Fasting
- Meals
- Activity
- Sleep
- Weight / body trends
Section 02
Your Body Is Constantly Managing Energy.
Every moment of the day, your body is deciding how to use, store and access energy.
After a carbohydrate-containing meal, glucose becomes readily available and insulin helps coordinate its use and storage.
Between meals, during exercise, and during periods of lower energy intake, the body can increasingly draw on stored energy.
When conditions favour greater fat use, fatty acids become an important fuel. The liver can also convert some fatty acids into ketone bodies, which can be used by several tissues as an alternative energy source.
Learn the science — Insulin and glycogen
Insulin is a hormone released by the pancreas that helps coordinate how the body uses and stores nutrient energy after eating. Among other roles, it supports glucose uptake in some tissues and promotes storage pathways.
Glycogen is a stored form of glucose held mainly in the liver and skeletal muscle. Liver glycogen can contribute to circulating glucose between meals; muscle glycogen is used largely within the muscle itself.
Section 03
From Glucose to Fat and Ketones
- 01
Fed state
Dietary energy is readily available. Glucose utilisation and energy storage generally increase.
- 02
Between meals
As time passes after eating, insulin generally falls and stored energy becomes increasingly available.
- 03
Greater fat utilisation
Fatty acids released from stored fat can increasingly contribute to energy production.
- 04
Ketone production
Under conditions such as fasting, prolonged exercise or carbohydrate restriction, the liver can increase production of ketone bodies from fat.
- 05
Ketosis
Ketosis describes a metabolic state in which circulating ketone levels are meaningfully elevated.
Learn the science — Lipolysis, beta-oxidation and ketogenesis
Lipolysis describes the breakdown of stored triglycerides, releasing fatty acids and glycerol into circulation.
Beta-oxidation is the process by which fatty acids are progressively broken down inside mitochondria into units that feed into further energy-producing pathways.
Ketogenesis refers to the liver's production of ketone bodies from fatty acid-derived units, which can then be released into circulation.
Section 04
The Goal Isn't One Fuel. It's Flexibility.
Your metabolism is dynamic. Depending on food intake, fasting, physical activity, energy demand and individual physiology, the contribution of different fuels can change. The ability to adapt fuel use appropriately is often described as metabolic flexibility.
Overnight: as the hours since eating increase, stored energy generally contributes more.
Illustrative example — not medical guidance.
This gauge is an educational illustration, not a measurement. SugaTone does not directly measure fuel selection or metabolic flexibility.
Learn the science — Metabolic flexibility
Metabolic flexibility is a research concept describing how readily fuel use adjusts to changing availability and demand. In studies it is assessed with specialised laboratory methods, not with consumer tracking tools.
Illustrative example — not medical guidance.
Shapes are schematic. Direction, timing and magnitude vary substantially between people.Section 05
Ketones Tell Another Part of the Story.
Ketones are molecules produced primarily by the liver from fatty acids when conditions favour greater fat oxidation and ketogenesis. They can serve as an alternative energy source for several tissues, including the brain.
Ketone measurements can therefore provide additional metabolic context when considered alongside glucose, fasting duration, food intake, activity and other factors.
Section 06
Two Signals. One Additional Perspective.
The Glucose Ketone Index compares blood glucose, expressed in mmol/L, with blood ketones, also expressed in mmol/L.
GKI can provide another way of looking at the relationship between glucose availability and ketone production. It is not a diagnosis, it does not need to be low for everyone, and SugaTone does not set GKI targets or claim that any particular value treats or prevents disease.
See Your Metabolic Signals TogetherGlucose (mmol/L)
Ketones (mmol/L)
= GKI
Glucose: 5.0 mmol/L
Ketones: 1.0 mmol/L
GKI = 5.0
Illustrative example — not medical guidance.
Section 07
Your Cells Have a Recycling System.
Cells continuously maintain themselves.
One important cellular housekeeping process is called autophagy, a term derived from words meaning "self-eating". Through autophagy-related processes, cells can identify, break down and recycle certain damaged, unnecessary or dysfunctional cellular components. This contributes to cellular quality control and normal cellular function.
Nutrient availability, energy status and cellular signalling influence autophagy-related pathways. Fasting is scientifically interesting in this context, but the timing and magnitude of these processes in humans vary and cannot be inferred precisely from a fasting timer alone.
- 1Damaged or unnecessary cellular material
- 2Autophagosome
- 3Lysosome
- 4Breakdown
- 5Recycling of cellular components
Learn the science — Autophagy, AMPK and mTOR
AMPK and mTOR are cellular signalling components involved in sensing energy and nutrient status. They are frequently studied in relation to autophagy-related pathways.
Much of the detailed mechanistic work in this area comes from cell and animal models. How precisely these findings translate to specific fasting durations in individual humans is not settled, which is why SugaTone avoids hour-based autophagy claims.
Section 08
Meet the Mitochondria.
Tiny structures with an enormous job.
Mitochondria are structures inside most of our cells that play a central role in converting energy from nutrients into ATP, a form of energy cells can use. They participate in the metabolism of glucose-derived fuels and fatty acids and are central to the body's energy economy.
Learn the science — ATP and mitochondria
Nutrient-derived fuels are processed through several enzymatic steps before their energy is captured. Mitochondria host key stages of this process, ultimately supporting ATP production that powers cellular work.
- Glucose / fatty acids
- Metabolic pathways
- Mitochondria
- ATP
- Cellular work
Section 09
Fasting Is a Transition, Not a Stopwatch Competition.
- 0h
Recently fed
Dietary nutrients are still influencing energy availability.
- 12h
Between meals
The body increasingly draws on stored energy as recently absorbed nutrients decline.
- 16h – 20h
Longer fasting
For many people, fat utilisation and ketone production may increase as fasting continues.
- 24h+
Individual response
The timing and magnitude of these changes vary substantially between people.
Factors that shape individual response
- Previous meals
- Carbohydrate intake
- Physical activity
- Glycogen availability
- Insulin sensitivity
- Sleep
- Medications
- Metabolic health
- Individual biology
Section 10
Metabolic Health Belongs to Everyone.
You don't have to wait until something is wrong to become curious about how your body works. SugaTone is designed for adults who want a clearer view of the patterns connecting their everyday choices with their metabolic data.
- Glucose patterns
- Ketones
- Fasting
- Nutrition
- Activity
- Sleep
- Weight trends
- Metabolic flexibility
SugaTone gives you a place to bring those signals together. It is a tool for curiosity, education and informed self-observation — not a screening, diagnostic or preventive medical device.
A Number Without ContextIs Just a Number.
- Meals influence it.
- Movement influences it.
- Sleep influences it.
- Fasting influences it.
- Stress may influence it.
- Your individual biology influences it.
SugaTone helps you see the connections.
Understand Your Numbers. Discover Your Patterns. Take Control.
Your metabolism is telling a story. SugaTone helps you start understanding it.
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Scientific Sources & Further Reading
The explanations on this page are written at the level of widely taught, textbook physiology and are deliberately kept conservative. Specific citations have not been added here because they have not yet been independently verified for this page.
This section is reserved for a subsequent evidence-review pass, in which verified references will be listed. No citations, authors, journals or identifiers have been invented.