Burning Body Fat vs. Dietary Fat: 8 Surprising Insights
Your body can burn fat for energy… but is it burning the fat you eat, or the fat you've been storing?
We hear plenty about eating less, moving more and burning calories - but how often do we think about how our bodies actually choose which fuel to use?
And here's another curious question: If we have plenty of stored body fat, why do we still experience hunger, fatigue and cravings throughout the day instead of simply drawing on those energy reserves?
It's a fascinating part of metabolism that deserves a much closer look.
From his latest read, Bill has been exploring the relationship between dietary fat, stored body fat, insulin, hormones and our body's ability to switch between energy sources.
Here are eight insights that might change the way you think about burning fat, managing energy and supporting your long-term health.
1. Burning Fat Doesn't Necessarily Mean Burning Body Fat
Burning fat and losing body fat sound like the same thing, but there's an important distinction.
Our bodies have access to fat from two main sources:
Dietary fat: The fat we consume through foods such as eggs, avocados, olive oil, nuts, dairy and meat.
Stored body fat: Energy our bodies have tucked away in fat cells for future use.
Both can provide fuel, but here's the catch: Just because you're burning fat doesn't necessarily mean you're reducing your body fat stores.
If your body is using fat from your latest meal for energy, that's still fat burning. It just doesn't automatically translate into losing stored body fat.
To reduce those reserves over time, your body generally needs to use more energy than it takes in.
Bill's biggest takeaway: Just because your body is using fat for energy doesn't mean it's tapping into its reserves.
2. Your Body Has a Fuel-Switching System
One of the remarkable things about our bodies is how adaptable they are.
We can produce energy using glucose from carbohydrates or fatty acids from fat, depending on what's available and what our bodies need.
This ability to move between fuel sources is called metabolic flexibility.
Think about what happens throughout a typical day. After a meal, particularly one containing carbohydrates, our bodies tend to use more glucose. Between meals, during fasting or certain types of exercise, fat use can increase.
But what happens when we become less efficient at making that switch?
That's where things get interesting.
When metabolic flexibility is impaired, the body may have more difficulty adjusting between available fuel sources. Hunger, cravings and fluctuating energy levels can become more noticeable, although several factors can contribute to those symptoms.
Bill's takeaway: Improving our ability to switch between fuels could be an overlooked piece of the weight-management puzzle.
3. Insulin: The Gatekeeper to Your Stored Body Fat
Think of insulin as one of the body's fuel managers.
After we eat, insulin helps our cells take in glucose and signals the body to prioritize using and storing incoming nutrients rather than releasing stored fat.
As insulin levels fall, those fat reserves become more accessible for energy.
It's a natural process that helps us manage fuel throughout the day.
But what happens when insulin levels remain elevated or our cells stop responding to it effectively?
That's where insulin resistance enters the picture.
When cells become less responsive to insulin, the body may need to produce more of it to manage blood sugar. Over time, this can interfere with normal fuel regulation and the body's ability to switch efficiently between glucose and fat.
When Energy Metabolism Breaks Down: The Connection to Diabetes
One of the more interesting connections explored in Bill's latest read is the relationship between insulin, our ability to access stored fat and diabetes.
Diabetes isn't simply about having too much sugar in the blood. It's also a disorder of energy metabolism, affecting how our bodies use, regulate and store fuel.
Insulin is central to this process. It helps glucose enter muscle and fat cells, regulates energy storage and influences the release of stored body fat.
When these systems become disrupted, several problems can develop:
Insulin resistance: Cells become less responsive to insulin, making blood sugar more difficult to regulate.
Reduced metabolic flexibility: The body may become less efficient at switching between glucose and fat for energy.
Hypoglycemia: Blood sugar drops too low, potentially causing shakiness, weakness, hunger or confusion. This is particularly relevant for people with diabetes who use insulin or certain blood sugar-lowering medications.
Type 2 diabetes: Insulin resistance, combined with the body's inability to produce enough insulin to meet its needs, results in persistently elevated blood sugar.
There's also an important distinction between the two main types of diabetes.
Type 1 diabetes involves an absolute or near-absolute insulin deficiency, while Type 2 diabetes generally develops through insulin resistance and a progressive inability to produce sufficient insulin.
Diabetes doesn't mean the body loses its ability to burn fat. In fact, severe insulin deficiency can cause excessive fat breakdown. The problem is that the body's systems for managing and using energy are no longer functioning normally.
The bigger picture is that glucose metabolism, fat metabolism and insulin regulation are closely connected. When these systems aren't working together efficiently, the effects can extend well beyond blood sugar alone.
The takeaway: Healthy metabolism isn't simply about how much sugar or fat we consume. It's about how effectively our bodies regulate, store and access energy, and why maintaining insulin sensitivity matters for long-term metabolic health.
4. All That Stored Energy. So Why the Cravings?
Here's a situation many of us can relate to.
You grab a muffin and coffee for breakfast, get on with your morning and, an hour or two later, you're hungry again.
Wait a minute. Doesn't your body already have energy stored away?
Of course it does. So why are you looking for another snack?
This is where blood sugar, insulin and our ability to access different fuels become particularly interesting.
A breakfast (the WORST meal of the day to eat carbs!) dominated by refined carbohydrates can produce a relatively quick rise in blood sugar, followed by a decline. For some people, that pattern contributes to hunger, cravings or an afternoon slump.
Now compare that with a breakfast containing protein, fibre and some healthy fat. That combination generally takes longer to digest and may help keep you satisfied for longer.
Let's Not Forget Cortisol
There's another interesting piece of the morning energy puzzle: cortisol, the hormone that naturally rises as we wake up.
Produced by the adrenal glands, cortisol helps make glucose available to prepare the body for the day ahead.
When we follow that natural morning rise with a breakfast high in refined carbohydrates, blood sugar and insulin can rise further. The response varies from person to person, but it highlights how our hormones and food choices work together.
This is why the book places particular emphasis on avoiding refined carbohydrates first thing in the morning.
Rather than relying on a quick pastry or carby, sugary breakfast, consider starting the day with protein, fibre and healthy fats to support a steadier release of energy.
Bill's takeaway: Building on our last article about protein at breakfast, the foods we choose can influence not only how much energy we consume, but how satisfied and energized we feel afterward. Something worth remembering the next time you're planning breakfast or grabbing something on the go!
5. Your Brain Is an Energy Hog. Here's How It Gets Fuel.
Thinking takes fuel, and your brain needs plenty of it.
Although it accounts for only about 2% of your body weight, your brain uses approximately 20% of your body's resting energy. That's a considerable amount for an organ weighing just a few pounds!
Most of the time, glucose is its primary fuel. But our bodies have another option: ketones. When carbohydrate availability is reduced, the liver can convert fatty acids into ketones, which the brain can use for energy.
This becomes particularly important during fasting or prolonged carbohydrate restriction, when our bodies adapt by producing and using more ketones.
Here's where stored body fat comes back into the conversation: Fatty acids released from our body's energy reserves can help the liver produce ketones, providing an alternative source of fuel for the brain.
It's another example of how adaptable our metabolism can be. These processes also reinforce the importance of healthy blood sugar regulation and the complex relationship between insulin, energy availability and brain function.
Bill's takeaway: Our bodies have alternative energy systems, and understanding how they work offers a fascinating perspective on metabolism and fat burning.
6. Your Mitochondria: Why the Type of Fat You Eat Is So Important
Deep inside our cells are tiny structures called mitochondria, often described as the body's energy-producing machinery. Their job is to help convert nutrients from carbohydrates and fats into usable energy, keeping our cells functioning and our bodies moving.
But there's another consideration raised in Bill's reading: Does the type of fat we consume influence how well these energy-producing systems work?
There’s a big difference between fats that resist oxidation and those that break down more easily:
Saturated fats: Found in foods such as coconut and cheese, these fats are generally more chemically stable and resistant to oxidation.
Vegetable and seed oils: Canola, corn and soybean oils are concerns because of their polyunsaturated fatty acid content, particularly omega-6.
Oxidation and free radicals: Oxidation of less stable fats can produce reactive compounds that may contribute to cellular damage and inflammation.
Insulin and leptin resistance: Current research explores a possible connection between excessive omega-6 consumption, inflammation and disrupted metabolic and appetite signalling.
Stored body fat: Fatty acids from vegetable oils can accumulate in body fat and become difficult to eliminate, potentially interfering with normal fat metabolism.
As a result, Bill recommends reducing processed vegetable and seed oils in favour of fats such as olive oil, avocado oil, coconut oil and tallow.
And there's another way we can support our mitochondria that deserves attention: regular physical activity. Exercise encourages the body to maintain and adapt its energy-producing systems, improving our capacity to use fuel more efficiently.
Bill's challenge: Think beyond how much fat you're eating. Consider the types of fats you consume, how they're prepared and what role they may play in your overall metabolic health.
Bill's takeaway: Healthy metabolism involves more than what we eat. Keeping our energy-producing systems active matters, too, and regular movement is one of the most valuable ways to support them.
7. Hormones, Appetite and Body Fat Work Together
By now, we're beginning to see that burning stored body fat isn't controlled by one single process. It's a coordinated effort involving several hormones, each with an important job to do.
Insulin influences glucose use, fat storage and fat release.
Cortisol helps regulate energy availability, particularly during the morning.
Leptin communicates information about our longer-term energy reserves.
Ghrelin helps signal when we're hungry.
Thyroid hormones influence metabolic activity throughout the body.
Leptin is particularly interesting - produced primarily by our fat cells, leptin helps tell the brain how much energy the body has stored. You might assume that having more stored body fat would automatically mean feeling less hungry. But it's not always that straightforward.
When the brain becomes less responsive to leptin, a condition known as leptin resistance, normal appetite regulation may become disrupted. And this becomes particularly relevant as we get older. Changes in muscle mass, physical activity, sleep and metabolic health can all affect how efficiently our bodies manage energy.
It's one reason appetite and weight management can feel far more complicated than simply counting calories. Energy balance still matters, but there are many biological and behavioural factors influencing both sides of that equation.
Bill's takeaway: Supporting metabolic health means looking at the whole body, certainly not just the number on the scale.
8. Five Rules to Support Better Fat Burning
So what can we take from all of this and apply to our everyday lives?
Bill outlines five rules focused on the types of fats and carbohydrates we consume, hydration, essential minerals and nutritional support.
Rule #1: Avoid Vegetable and Seed Oils
Not all fats behave the same way, and one important difference is their susceptibility to oxidation - a chemical reaction that can produce compounds capable of damaging cells.
Saturated fats, such as those found in coconut oil and tallow, are generally more resistant to oxidation. Polyunsaturated fats, including omega-6 fatty acids found in many vegetable and seed oils, are more susceptible.
Based on this distinction, Bill recommends avoiding canola, corn and soybean oils, favouring olive oil, avocado oil, coconut oil and tallow instead.
While the broader health implications of these fats depend on more than oxidation alone, the central idea is to pay closer attention to the fats we're consuming, how they're prepared and their role in our overall diet.
Rule #2: Choose Slow-Digesting Carbohydrates
We've already explored how blood sugar and insulin influence our body's use of energy. This rule brings that discussion back to the foods on our plates.
Refined starches and sugary foods are often digested quickly, producing a relatively rapid rise in blood glucose.
Slower-digesting carbohydrates, particularly those rich in fibre, generally produce a more gradual response.
Interesting fact: The glycemic index measures how quickly carbohydrate-containing foods raise blood sugar on a scale of 0 to 100. Foods scoring 55 or below are considered low glycemic, while those scoring 70 or above are high glycemic.
Think vegetables, lentils, beans and minimally processed whole grains rather than relying heavily on refined breads, pastries and sugary snacks.
The goal is to support steadier blood sugar, better appetite regulation and the body's natural ability to switch between glucose and fat for energy.
Rule #3: Seek Salt
Salt does much more than add flavour to our food.
Sodium is an essential electrolyte involved in nerve signalling, muscle contractions and fluid balance. Without enough of it, our muscles and nerves simply can't function normally.
Bill's latest read highlights Celtic sea salt and Himalayan pink salt, along with a proposed connection between sodium intake and insulin resistance.
Adequate sodium is important, particularly when we're losing electrolytes through heavy sweating. However, increasing salt intake has not been shown to reverse insulin resistance, and excess sodium can raise blood pressure.
The key is maintaining an appropriate electrolyte balance for your individual needs.
Rule #4: Drink Water
Here's something to keep in mind - our bodies are approximately 60% water.
Water is involved in nearly every major process that keeps us functioning, from circulation and temperature regulation to nutrient transport and waste removal. It also provides the environment in which countless cellular reactions take place.
Interesting fact: The proportion of water in our bodies changes with age and body composition. Older adults generally have a lower percentage of total body water, largely because of changes in lean muscle mass and body fat.
Making hydration a regular part of your day is one of the simplest habits you can build. Keep water nearby, adjust your intake for activity and temperature, and if plain water doesn't appeal to you, try adding lemon, cucumber or fresh mint.
Sometimes the easiest changes are the ones we're most likely to stick with!
Rule #5: Supplement Smartly
Vitamins and minerals do much more than fill nutritional gaps! They're involved in the processes that help us produce energy, maintain muscle and regulate metabolism.
Four nutrients deserve particular attention:
Vitamin D3: Supports calcium absorption, bone health and normal muscle function.
Magnesium: Essential for energy production, muscle contractions and blood glucose regulation.
Zinc: Supports immune function, protein synthesis and cellular repair.
Iodine: Required to produce thyroid hormones, which help regulate metabolic activity throughout the body.
Interesting fact: Magnesium participates in more than 300 enzyme systems, including those involved in energy production and blood glucose control.
And here's another interesting connection: People following vegan diets may be more vulnerable to inadequate iodine intake because dairy, seafood and eggs are common dietary sources.
The goal isn't to take more supplements simply for the sake of it. It's to make sure the body has the nutrients it needs, identifying and addressing gaps where appropriate.
Taken together, these five rules encourage us to think more carefully about the everyday choices that influence how our bodies produce, store and use energy.
But there's one more habit that deserves special attention.
Keep moving!
Walking, resistance training and regular exercise help improve insulin sensitivity, preserve muscle and support metabolic flexibility.
For adults over 40, maintaining muscle and staying physically active are particularly valuable investments in long-term health.
Bill's takeaway: Supporting your metabolism doesn't have to involve dramatic changes. Consistent daily habits can make a meaningful difference, and it starts with a little more awareness of how our whole body works. Curious to know more? Make a plan with Bill!
So, Are You Burning Fat or Accessing Stored Fat?
If there's one idea to take away from these eight insights, it's this:
Burning fat and losing stored body fat aren't necessarily the same thing.
Our bodies are constantly managing incoming energy, stored energy, hormones and cellular demands. Dietary fat can provide fuel. Stored body fat can provide fuel. Carbohydrates can provide fuel. And our bodies have remarkably sophisticated systems for deciding how and when to use them.
The more we understand these processes, the better equipped we are to make informed choices about food, movement and metabolic health.
It's also a reminder that healthy aging isn't just about eating less or watching the number on the scale. It's about maintaining the strength, energy and physical ability to continue doing the things we enjoy.
The goal isn't simply to burn more calories - it's to build a body that uses energy efficiently, stays strong and supports us through the years ahead.
Keep moving, stay curious and keep learning!
— Bill DeHoog