Metabolic Health: How LCHF, Keto or Fasting Increase Energy & Fat-Loss
Optimizing metabolic health through strategic dietary approaches like fasting and low-carbohydrate diets enhances energy production while improving key metabolic markers including blood glucose levels. These metabolic pathways promote efficient fat metabolism, allowing the body to achieve metabolic flexibility that supports sustained energy levels and effective fat-loss.
What is Metabolic Health?
The metabolism functions to create energy from the nutrients one consumes. Metabolic health is about maintaining healthy metabolic markers like blood glucose, insulin, cholesterol, triglycerides, and blood pressure, while creating energy from food, efficiently.
Disrupting metabolic function leads to an increased risk of metabolic syndrome, a cluster of physical conditions related to obesity, diabetes, and heart disease. One common thread for metabolic dysfunction is poor blood glucose regulation, (1) partly due to a poor diet high in refined carbohydrates.
A key factor in enhancing metabolic health is training the body’s ability to switch to fats for fuel, instead of predominantly relying on carbohydrates. This so-called metabolic flexibility enhances the utilization of energy which in turn reduces the metabolic strain on the body while improving metabolic markers. (2)
Beyond exercise, the most effective dietary approaches proven effective for metabolic health include fasting, calorie restriction, and keto diet. Most rely on reducing the total amount or frequency of carbohydrates consumed.
How do you increase your metabolic health?
To improve metabolic health:
Diet
- Intermittent fasting (16/8 is beginner-friendly)
Cut back on sugar and refined carbs - Eat more vegetables, protein, and healthy fats
- Consider low-carb diet, or extend fast with keto breakfast
Movement
- Combine strength training and cardio exercise
- Try HIIT workouts for better insulin sensitivity
- Reduce sitting time with regular movement breaks
Lifestyle
- Get 7-9 hours of quality sleep
- Manage stress through meditation or mindfulness
- Try cold exposure (cold showers)
Helpful additions
- Consider supplements like berberine or magnesium (with doctor approval)
- Use apple cider vinegar before meals
- Monitor your progress with regular health checks
What foods are best for metabolic health?
Foods that support metabolic health include:
Protein sources
- Fatty fish (salmon, mackerel, sardines) rich in omega-3s
- Grass-fed beef and pasture-raised poultry
- Eggs (particularly the yolks, rich in choline)
- Plant proteins like tempeh, tofu, and legumes (in moderation due to carb content)
Healthy fats
- Extra virgin olive oil (rich in oleic acid)
- Avocados and avocado oil
- Nuts and seeds (especially walnuts, almonds, flaxseeds)
- MCT oil (medium-chain triglycerides that support ketone production)
- Coconut oil (in moderation)
Low-glycemic vegetables
- Leafy greens (spinach, kale, arugula)
- Cruciferous vegetables (broccoli, cauliflower, Brussels sprouts)
- Asparagus, zucchini, bell peppers
- Mushrooms
Low-sugar fruits
- Berries (blueberries, strawberries, raspberries)
- Avocados (technically a fruit)
- Green apples
Other beneficial foods
- Fermented foods (kimchi, sauerkraut, kefir) for gut health
- Herbs and spices (cinnamon, turmeric, ginger) with anti-inflammatory properties
- Apple cider vinegar (improves insulin sensitivity)
- Green tea (contains beneficial catechins)
- Dark chocolate (70%+ cacao, in moderation)
Foods to limit or avoid
- Refined carbohydrates and added sugars
- Processed vegetable oils high in omega-6 fatty acids
- Ultra-processed foods (UPFs) with artificial ingredients
- Alcohol (particularly sugary mixed drinks)
- Sweetened beverages
The ideal metabolic health diet emphasizes whole, unprocessed foods with adequate protein, healthy fats, fiber, and limited refined carbohydrates.
How does exercise improve metabolic health?
Exercise improves metabolic health in several important ways:
Blood sugar
- Muscles absorb more glucose, even without insulin
- Improves insulin sensitivity
- Creates “storage space” for glucose by using up glycogen
Energy production
- Increases cellular power plants (mitochondria)
- Helps your body burn fat more efficiently
- Improves ability to switch between using sugar or fat for fuel
Body changes
- Builds muscle, which burns more calories even at rest
- Reduces harmful belly fat around organs
- Improves heart health and blood pressure
Different exercises work in complementary ways
- Strength training builds metabolically active muscle
- Cardio improves heart health and fat burning
- HIIT workouts are especially good for insulin sensitivity
- Even just walking after meals helps control blood sugar
6 Metabolic Health Markers
Metabolic markers are often used to assess the metabolic health and function of an individual. Having ranges within the normal zone is associated with better health, increased energy, and healthier body weight.
Blood Glucose Levels
Reflects how well one manages blood glucose. Elevated levels or high glycemic variability are associated with metabolic diseases like diabetes.
- Fasting blood glucose: 70-100 mg/dL
- Postprandial (2 hours after eating): <140 mg/dL
HbA1c or Glycated Hemoglobin
A blood test that gives a 3-month average of blood sugar levels, providing insight into long-term glucose regulation. The levels showcase how much glucose is attached to hemoglobin, the protein in red blood cells that carries oxygen.
- Normal levels 5-5.7%
- Prediabetes: 5.7%-6.4%
- Diabetes >6.5%
Insulin Sensitivity
Indicates how effectively cells respond to insulin. Poor insulin sensitivity is a hallmark of metabolic syndrome and type 2 diabetes. It is measured by:
- Fasting insulin levels: 2-10 μIU/mL (healthy) with some data showing 5-15 μIU/mL (normal)
- HOMA-IR – ≤1.0–2.0 (normal range); higher means lower insulin sensitivity
Cholesterol
Imbalances in lipids are associated with an increased cardiovascular risk. There’s high variance amongst experts on the nuances in what’s the optimal cholesterol profile, but generally higher HDL, lower TC, triglycerides, and LDL-C are considered healthier.
- HDL (High-Density Cholesterol): ≥40 mg/dL for men, ≥50 mg/dL for women (optimal ≥60 mg/dL)
- LDL (Low-Density Cholesterol): <100 mg/dL (optimal)
- Triglycerides: <150 mg/dL (optimal <100 mg/dL)
- Total Cholesterol: <200 mg/dL
Blood Pressure
It measures the force on the wall of your arteries. Generally, healthy levels seem to be around 120/80, while elevated blood pressure is a risk factor for cardiovascular disease.
- Healthy range: ≤120/80 mmHg
- Elevated Blood Pressure: 120–129/<80 mmHg
- Hypertension: >130/80 mmHg
Body Fat and BMI
Being at a healthy weight is critical to longevity, and it gives a comprehensive picture into metabolic health. BMI takes muscle % into account as well, instead of total body weight, which is more accurate.
- BMI: 18.5-24.9 (healthy range)
- Body Fat: men 10-20%; women 20-30%
How do you define metabolic health?
Metabolic health is about effective energy creation without significant fluctuations in glucose. It is typically measured by measuring the five key metrics, including fasting glucose, HbA1c, and insulin sensitivity.
What are the five measures of metabolic health?
- Blood Glucose Levels: Indicates how well your body regulates blood sugar.
- HbA1c: Provides a long-term view of blood sugar control.
- Insulin Sensitivity: Reflects how efficiently your cells respond to insulin.
- Cholesterol: Assesses lipid balance and cardiovascular risk.
- Blood Pressure: Measures arterial force, an important indicator of cardiovascular health.
Fasting and Low-Carb Diet On Metabolic Health
Insulin levels rise with glucose consumption to store glucose into other tissues. Overconsumption of carbohydrates (quick-energy) one doesn’t use is stored as excess fat tissue. Beyond increasing inflammation, chronically elevated insulin is detrimental to metabolic function, aging, and stimulates hunger, making weight loss very difficult.
One common trait of various dietary approaches like calorie restriction, ketogenic diet, or even intermittent fasting is reducing glucose consumption. This depletes glycogen stores which stimulates the liver to start breaking fats into ketones, as an alternative source of energy. (3)
Most components of metabolic syndrome like obesity, fasting blood sugar, high TG, and hypertension seem to be improved with such dietary approaches, signaling the importance of improving tolerance to carbs. (1)
Once the metabolic switch is activated and the body starts producing ketones, numerous beneficial effects occur. Insulin sensitivity improves, energy levels are increased, fat loss occurs faster, and metabolic markers improve.
Is low-carb good for metabolic syndrome?
Yes, low-carbohydrate diets can be beneficial for metabolic syndrome. By reducing carbohydrate intake, especially refined carbs and sugars, low-carb diets help lower insulin levels and improve insulin sensitivity. This dietary approach depletes glycogen stores, stimulating the liver to produce ketones from fat, which serves as an alternative energy source.
Research indicates that low-carb diets improve multiple components of metabolic syndrome, including:
- Reduced fasting blood glucose
- Improved triglyceride levels
- Decreased blood pressure
- Enhanced weight management
- Improved HDL cholesterol levels
The metabolic benefits stem primarily from reduced insulin levels and improved glucose regulation.
Is fasting good for metabolic health?
Yes, fasting appears to be beneficial for metabolic health through multiple mechanisms:
- Extends the period of low insulin, improving insulin sensitivity
- Activates the metabolic switch to fat metabolism and ketone production
- Reduces inflammation and oxidative stress
- Improves hunger hormone signaling (leptin/adiponectin ratio)
- Enhances mitochondrial function through hormesis
- Increases gut microbiota diversity
Research has shown that various fasting protocols (intermittent fasting, time-restricted eating, etc.) can improve metabolic markers like fasting glucose, HbA1c, insulin levels, and lipid profiles. Fasting creates periods of metabolic rest that allow cellular repair mechanisms to activate, potentially contributing to longevity benefits as well.
What are healthy fasting glucose levels?
Normal fasting glucose levels are considered between 70 mg/dL (3.9 mmol/L) and 100 mg/dL (5.6 mmol/L), however, the majority of the data favors fasting glucose in the lower band at 72-85 mg/dL for optimal health outcomes.
4 Benefits of Fasting or Low-Carb Diet
Reducing the total amount or frequency of sugar consumption is associated with improvements in metabolic health. Scanning the data, it’s evident that the main mechanism behind improvements in metabolic function greatly relies on reducing insulin levels.
Glycemic Control
Maintaining stable blood glucose levels is a key component of metabolic health. While blood sugar will naturally rise and fall throughout the day, keeping glucose movements in a healthy range is critical.
Most experts agree that 70 – 120 mg/dL is a healthy range for blood glucose during the day, and it should rarely exceed 140 mg/dL. Both hypoglycemia and hyperglycemia are detrimental to one’s health.
Fast glucose spikes and drops seem to contribute to inflammation and metabolic diseases.
The data shows a clear link between dietary restriction of carbohydrates and improved glycemic control. Particularly, approaches like fasting, ketogenic diet, or calorie restriction seem to improve insulin sensitivity and reduce the risk of metabolic issues. (4) (5) (6)
Alongside improved markers like fasting blood glucose, HbA1C, insulin plasma levels; glucose restriction can bring forth positive metabolic adaptations, improve lipid profile (increase HDL, decrease LDL-C and TG), and enhance fat loss. (1) (5) (7) (8)
Beyond fasting or carb-limiting, other ways to enhance glycemic control include:
- Shifting from simple high-GI foods to complex, low-GI carbohydrates richer in fiber like lentils, green leafy vegetables, oats, peas, seeds, and berries.
- Eating foods rich in protein and healthy fats alongside carbs to balance the insulin response
- Adding nutrients like berberine, alpha-lipoic acid, apple cider vinegar, or chromium picolinate have shown insulin-balancing effects
Glycemic control is tightly connected to insulin sensitivity. The better the cells recognize insulin, and the more insulin one can secrete, the easier it is to manage blood glucose. Fasting or keto, by reducing carbohydrate intake, reduces the strain on the pancreas which in turn improves insulin sensitivity.
Energy Levels
The stimulation of fat metabolism can enhance energy creation at a cellular level. This mechanism allows the body to transition to fats for fuel effectively, thus reducing reliance on glucose.
Ketones are also more energy efficient, meaning they produce more ATP molecules and less free radicals compared to glucose. (9)
Moreover, ketosis or fasting can stimulate mitochondrial function via a process called mithormesis. Essentially, relying on ketones (BHB) which are elevated during ketosis stimulate mitochondrial respiration which is key in upregulating their function. Mitochondria are the aerobic hubs of life responsible for creating ATP the body can use. (10) (11)
It seems that reducing glucose intake can improve the metabolism of glucose and lipids, promoting metabolic efficiency. This improves the energy creation machinery in the body, which brings forth longer lasting, sustainable energy that the body can tap into.
Weight Loss
Losing weight is determined by calorie expenditure. Consuming fewer calories than one burns will result in weight loss. Beyond calorie restriction, strategies like fasting and keto introduce the element of metabolic flexibility which can play a significant role in weight management.
Essentially, hunger and energy levels strongly dictate one’s appetite. Relying solely on carbohydrates decreases metabolic efficiency, which in turn decreases energy. This loop of fatigue is solved by eating more glucose.
It’s evident that excess glucose increases inflammation and oxidative stress, being detrimental to glucose transport, mitochondria, and metabolic function. (12) (13) (14)
Fasting, by extending the non-glucose window:
- improves metabolic markers like fasting glucose, adiponectin, and insulin sensitivity (15) (16)
- increases gut microbiota diversity (17)
- improves hunger-hormone signaling (ratio of leptin/adiponectin) (18)
- increases ketone use, due to which fat loss occurs (19)
Such micro effects accumulate and shift the metabolism to create energy more efficiently, which partially solves the problem of hunger and fatigue, addressing the root cause of weight gain.
Most of the data links carbohydrate restriction, whether via keto, fasting, or calorie restriction to net positive outcomes for fat loss and weight management. (19) (20) (21) (22) (23) (24)
Inflammation
High-carbohydrate diet stimulates anabolism. It’s a state of high insulin, high glucose that supports muscle growth, weight gain, and other anabolic pathways. Anabolism is essential, but overly elevated insulin state leads to increased inflammation.
On the reverse, catabolic diets like fasting or calorie restriction promote cellular breakdown. During it, ketones are elevated and insulin is low, resulting in fat loss. This shift tends to reduce inflammation and oxidative stress, partly because of the lower amount of free radicals produced by ketones.
Neither is good or bad. Maintaining a balance is essential. However, this understanding explains the reason calorie restriction has been linked to anti-aging and longevity. Additionally, fasting has also been linked to lower DNA damage, preservation of telomeres, and slower aging. (25) (26) (27) This showcases the narrative of taking less hits or reducing metabolic strain to be longevity-promoting.
The research shows fasting and keto-mimicking diets to reduce markers of oxidative stress, inflammation, and improve antioxidant capacity. (28) (29) (30) This way the body trains to neutralize oxidative damage.
BHB, the most studied ketone body is elevated during ketosis. BHB is known to improve mitochondrial respiration, thus stimulating the endogenous antioxidant system in the body. (31)
How metabolic health affects weight loss?
Metabolic health significantly impacts weight loss through several interconnected mechanisms:
- Insulin sensitivity: Better insulin sensitivity means less insulin is needed to manage blood glucose, reducing fat storage signals and making stored fat more accessible.
- Metabolic flexibility: The ability to switch between carbohydrate and fat metabolism enables more efficient access to fat stores when needed.
- Energy efficiency: Improved mitochondrial function creates more energy from less food, reducing fatigue-driven hunger.
- Hormonal balance: Healthier metabolic function improves hunger hormone signaling (leptin/ghrelin/adiponectin), better regulating appetite and satiety.
- Inflammation reduction: Lower inflammation removes a barrier to effective fat metabolism.
- Glucose stability: Stable blood sugar prevents energy crashes that trigger hunger and cravings.
Can an obese person be metabolically healthy?
Yes, it is possible for an obese person to be metabolically healthy, a phenomenon sometimes called metabolically healthy obesity (MHO). These individuals maintain normal blood pressure, blood glucose, insulin sensitivity, and lipid profiles despite having elevated BMI or body fat percentage.
However, research suggests that:
- MHO is relatively uncommon, affecting about 10-30% of obese individuals
- It may be a transitional state rather than a stable condition
- Long-term studies indicate many metabolically healthy obese individuals eventually develop metabolic abnormalities
- Even with normal metabolic markers, obesity itself carries independent health risks
Does obesity affect metabolism?
Yes, obesity significantly affects metabolism in several key ways
- Insulin resistance: Extra fat tissue makes cells less responsive to insulin, keeping blood sugar high
- Hormonal imbalance: Disrupts hunger and fat-storage hormones like leptin
- Reduced energy production: Impairs mitochondria (cellular energy generators)
- Increased inflammation: Creates low-grade inflammation throughout the body
- Fat-burning difficulty: Makes it harder to use stored fat for energy
These changes create a cycle where weight management becomes increasingly difficult as the body resists fat-burning and favors fat storage.
Does metabolism affect energy levels?
Yes, metabolism significantly affects energy levels. Efficient metabolic function ensures:
- Optimal ATP production (cellular energy currency)
- Better mitochondrial function
- Improved metabolic flexibility (switching between fuel sources)
- Stable blood glucose and insulin levels
When metabolic health is poor, several factors can reduce energy:
- Blood sugar fluctuations cause energy crashes
- Mitochondrial dysfunction reduces ATP production
- Inflammation increases energy expenditure on immune responses
- Insulin resistance prevents efficient glucose utilization
- Poor fat metabolism limits access to stored energy
Ketones are generally more energy-efficient than glucose, producing more ATP molecules with fewer reactive oxygen species, potentially contributing to sustained energy levels.
How does a low-carb diet affect one’s energy levels?
A low-carb diet can affect energy levels in several ways. Initially, some people may experience fatigue as their bodies adapt to using fat for fuel instead of glucose. However, once the body becomes more efficient at burning fat, many individuals report more stable and sustained energy levels throughout the day. This is because fats and ketones provide an alternative or rather additional, being supportive in times of low glucose availability.
How does insulin affect blood sugar levels?
Insulin is the primary hormone responsible for regulating blood glucose levels. When you consume carbohydrates, they’re broken down into glucose, which enters the bloodstream. The pancreas then releases insulin, which:
- Enables glucose uptake into cells (especially muscle and fat cells) by activating GLUT4 transporters
- Promotes glycogen storage in the liver and muscles
- Inhibits glucose production (gluconeogenesis) by the liver
- Stimulates fat storage when excess glucose is present
- Suppresses lipolysis (fat breakdown)
Without adequate insulin or with insulin resistance, glucose remains in the bloodstream, leading to hyperglycemia. Chronically elevated insulin levels (hyperinsulinemia) can eventually cause cells to become less responsive to insulin signals, creating a vicious cycle of insulin resistance that requires even more insulin to maintain blood glucose control.
What is a healthy fasting insulin level?
A healthy fasting insulin level typically ranges from 5 to 15 μIU/mL. Levels above this range may indicate insulin resistance, while consistently elevated levels (hyperinsulinemia) are associated with metabolic syndrome, prediabetes, and type 2 diabetes.
How to Improve Metabolic Health
Training the body to tap into fat for fuel is the primary way one can gain metabolic flexibility. Oftentimes this is linked to improvements in metabolic markers like fasting glucose, insulin sensitivity, blood pressure, and lipid profile.
Exercise, cold exposure, and deep sleep all contribute to better metabolic health. In terms of dietary approaches one can experiment with, here’s the list.
Fasting
Intermittent fasting on a daily basis of 16/8 hours effectively restores glucose metabolism and aids in improving metabolic function, due to the extended fasting phase. One of the most practical, sustainable, and recurring methods.
Keto Breakfast
Instead of skipping breakfast, one can extend the fasting from sugar window by making the first meal of the day ketogenic. This way the body can tap into fat stores and activate the metabolic switch, without the need of lengthening the fasting window.
MCT Coffee
Caffeine can promote ketosis faster, especially in low-glucose environments. Exogenous ketones can further speed up the transition to ketosis, which is why adding MCT to coffee is a well-known biohack to promote mental clarity and fat loss.
Metabolic Plate
Just reducing the amount of simple high-GI carbs in one’s diet, swapping for low-GI foods, complex carbohydrates high in fiber does the heavy lifting. Additionally, increasing the amount of protein and fiber significantly improves glycemic control and reduces blood glucose spikes.
The metabolic plate can look something like this:
- Chicken tights with black lentils and broccoli
- Beef patties with sweep potato and eggs
- Salmon with lemon juice, asparagus, and mushrooms
- Buckwheat cooked with butter, zucchini, and cheddar cheese
Glucose Tracking
Monitoring glucose levels consistently gives a great insight into how the foods we eat impact glucose levels. This gives specific guidance for improving meal timing, macronutrient composition, and food choices based on individual responses.
Glucose Stabilizing Agents
There are specific nutrients that have been shown to improve glucose control.
- Berberine is one such powerful compound extracted from plants.
- Magnesium is involved in glucose and insulin metabolism.
- ALA or alpha-lipoic acid, an antioxidant that enhances glucose uptake.
- Chromium picolinate may benefit post-meal glucose stabilization.
- Apple cider vinegar has been shown effective for metabolic function.
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