Whether you can lose weight on 40 net carbs per day depends on several factors like your current weight, insulin resistance, activity levels, genetics, and more. Some people may be able to successfully lose weight at this carb level while others may need to reduce carbs further for optimal fat loss.
What are net carbs?
Net carbs refer to the total carbohydrates in a food minus the fiber content. Fiber is subtracted because it is indigestible and does not impact blood sugar levels like other carbs.
To calculate net carbs, you subtract the grams of fiber from the total carbs. For example, if a food has 15g total carbs and 5g fiber, the net carbs would be 10g (15g – 5g = 10g).
Why limit net carbs for weight loss?
When you eat carbohydrates, your body converts them into glucose which raises blood sugar levels. The rise in blood sugar stimulates the release of insulin. Insulin is the hormone responsible for shuttling sugar from the bloodstream into the cells for energy.
However, insulin also signals the body to store fat. Higher levels of insulin may promote fat storage, especially around the belly. Limiting carb intake can help lower insulin levels, allowing for easier access to stored fat for energy.
In addition, very low carb and ketogenic diets work by depleting glucose stores. As glucose drops, the body enters ketosis – a state where ketone bodies produced by the liver become the main fuel source.
This metabolic switch from using glucose to ketones may turn the body into a “fat burning machine”, supporting greater natural fat loss.
What research says about low carb diets for weight loss
Many controlled trials show that carbohydrate restricted diets can be an effective weight loss tool:
- One study compared a ketogenic diet providing less than 50g net carbs per day to a low fat diet. After 24 weeks, those on the ketogenic diet lost over twice as much weight (11.1 lbs vs. 4.8 lbs) 
- In another trial, obese individuals lost more weight on a very low carb, ketogenic diet providing 20g of carbs per day compared to a calorie-restricted, low fat diet over a 24-week period. 
- Research also shows that lower carb diets result in greater improvements in waist circumference, triglycerides, blood sugar levels, and HDL cholesterol compared to low fat diets, even when the amount of weight loss is similar.
However, low carb diets may not be more effective for weight loss compared to moderate carb diets in all situations. When calories and protein are controlled, lower carb plans seem to work best for those who are insulin resistant or have metabolic syndrome.
Factors that affect weight loss on 40 net carbs
Several individual factors impact whether 40 net carbs per day will lead to weight loss:
Insulin resistant individuals tend to lose more weight on lower carb intake than those who are more insulin sensitive. This is because insulin resistant people secrete more insulin, promoting more fat storage.
Reducing carbs lowers insulin levels, allowing the body to access stored fat more effectively. Those with severe insulin resistance may require a stricter carb limit like 20-30 net grams to lower insulin and lose weight.
Weight and body fat percentage
People who have more weight to lose tend to shed pounds faster on low carb diets compared to those closer to their ideal weight. Those with significant weight to lose generally have more insulin resistance as well.
Additionally, very low carb diets seem most beneficial for those with higher body fat percentages. Leaner individuals may not lose weight as fast reducing carbs due to already having better insulin sensitivity.
If you are sedentary, a 40 net gram carb limit may help you lose weight. However, active individuals and athletes may struggle to get enough calories in on this intake. Higher activity levels have greater carb needs.
Active individuals can often eat more carbs while still losing fat because carbs are the preferred fuel source for muscles. The additional energy supports greater calorie burn during exercise.
Due to differences in hormones and metabolism, men may lose weight faster on lower carb intakes than women. Men tend to carry more weight as belly fat which responds quickly to carb restriction.
Women may experience stalled weight loss at very low carb intakes under 50g per day. Some may need to cycle between higher and lower carbs to optimally lose fat.
Genes impact how your body metabolizes and burns fat and carbs. People vary greatly in their response to carb restricted diets. While some thrive on keto and lose weight immediately, others lose just as well on higher carb.
The only way to know if you respond well to 40 net carbs or less is to test it. Genetics make general carb intake recommendations difficult.
How to determine your carb tolerance
Your personal carb tolerance depends on many factors like insulin sensitivity. Here are some steps to find your optimal range:
- Start tracking your diet for 1-2 weeks while eating normally. Don’t change anything, just be aware of your typical intake.
- Begin gradually reducing your carb intake over a few weeks while keeping protein and fat intake the same. Aim to lower daily carbs by about 20-30g each week.
- Watch for signs of low carb intolerance like fatigue, headaches, cravings, constipation. If they appear, you may have cut carbs too low. bump them up 5-10g until symptoms resolve.
- Stop lowering carbs when you see continued benefits like stable energy, appetite control, weight loss. Stay at this level for 1-2 months to see your new baseline tolerance.
- Adjust up or down 5-10g as needed if weight loss stalls or negative symptoms appear. Carb tolerance can change over time.
Tracking your body’s responses at different intakes can help identify your personal carb sweet spot for fat loss.
Foods to eat on a 40 net carb diet
Here are healthy low carb foods that can fit into a 40 net gram daily allowance:
Get your carbs from nutrient-dense, high fiber veggies like:
- Leafy greens – spinach, kale, lettuce
- Cruciferous veggies – broccoli, cauliflower, cabbage
- Green beans
High fat proteins
Prioritize fattier cuts of meat, fish, eggs, and dairy like:
- Chicken thighs and legs
Incorporate plenty of oils, nuts, seeds, avocados, and full fat dairy:
- Olive oil
- Coconut oil
- Nuts like almonds or macadamias
- Chia seeds
- Nut butters
Low carb fruits
Berries are the best low carb fruit options:
Remember to account for their carb counts in your daily total.
Herbs, spices, condiments
Flavor foods with:
- Hot sauce
- Apple cider vinegar
- Low carb marinades and dressings
Foods to avoid on a 40 net carb diet
Steer clear of these high carb options:
- Grains – bread, pasta, cereals, rice
- Starchy veggies – potatoes, corn, peas
- Legumes – beans, lentils, chickpeas
- Sweets – candy, baked goods, ice cream
- Fruit juices
- Packaged snacks
- Sweetened beverages
Sample meal plan
Here is a one day sample meal plan providing around 40g net carbs:
|2 eggs fried in 1 tbsp butter
1 oz cheddar cheese
1 cup black coffee
|Tuna salad made with 2 oz tuna, 1 tbsp mayo, mustard, pickles, lettuce
10 raw almonds
1 oz cheddar cheese
|6oz chicken breast
1.5 cups roasted broccoli
2 tbsp olive oil
Large salad with 2 cups mixed greens, 1/4 cup cherry tomatoes, 1 tbsp dressing
|1/4 cup blueberries
1 oz cheddar cheese
|~24g net carbs
Tips for success on a 40 net carb diet
Here are some tips to help you effectively lose weight on 40 net grams of carbs per day:
- Weigh and track your foods using an app to ensure accurate carb counting.
- Plan your meals so you aren’t caught needing to make poor carb choices.
- Carb count your recipes to know how they fit your daily needs.
- moderator protein at each meal, around 20-30g per meal.
- Eat fat for satiety like olive oil, butter, and avocado.
- Stay hydrated by drinking water, herbal tea, and bone broth.
- Get enough salt, magnesium, and potassium to feel energized and minimize low carb side effects.
- Move your body daily with walking, weights, yoga, or other activity you enjoy.
Drawbacks of a 40 net carb diet
Potential downsides of sticking to 40 net carbs or less include:
- Low energy, fatigue, headaches initially as the body adapts to using fat instead of glucose for fuel.
- Greater restrictions on fruits, starchy vegetables, and whole grains resulting in possible nutrient deficiencies long-term if foods aren’t replaced with quality low carb options.
- Constipation from lower fiber intake if consuming too much meat and cheese and not enough low carb veggies.
- Increased uric acid levels which can exacerbate gout.
- Bad breath and electrolyte imbalances if fluids and minerals aren’t replenished.
- Reduced athletic performance for those involved in high intensity activities or sports.
- Difficulty dining out or at social gatherings since most restaurant items and party foods contain too many carbs.
- Higher grocery bills since low carb specialty products can be expensive compared to grains, potatoes, beans, etc.
However, these potential issues can be prevented or minimized with some planning, supplementation, and balance.
Healthy carb cycling approach
While some may thrive on consistent very low carb intake, others may benefit from carb cycling periods of higher and lower daily carb allowances.
Carb cycling provides metabolic flexibility by alternating lower carb days with higher carb refeeds. It may help prevent plateaus, elevate leptin, replenish glycogen, and make dieting more sustainable.
An example carb cycling plan could be:
- 3 days at 30-50g net carbs
- 1 day at 100-150g net carbs
- 3 days at 30-50g net carbs
- 1 day at 100-150g net carbs
The lower and higher carb days can be cycled weekly or tailored to your training program. Carb cycling allows for metabolic and hormonal balance while still promoting fat loss.
Supplements to support low carb diets
The following supplements may help enhance results on a carb restricted diet:
Provides ketones and quick energy between meals. Can help reduce hunger and kickstart ketosis.
Ketone supplements boost blood ketone levels to mimic and enhance nutritional ketosis. Helpful during the adaptation phase.
Replenishes minerals lost through increased urination on low carb. Look for a source of sodium, potassium and magnesium.
Soluble fiber supplements like glucomannan can relieve constipation without raising carb intake.
Fish oil provides anti-inflammatory fats EPA and DHA. Useful for those reducing intake of omega-6s.
Supports healthy gut flora which can be altered on a low carb diet. May improve digestion and immunity.
Limiting net carbs to around 40g per day may help many people lose weight, especially those with significant weight to lose, insulin resistance, and/or high body fat percentages. However, some trial and error is required to find your own carb sweet spot for fat loss based on your unique metabolism, activity levels, and genetics.
Cutting carbs is not a magic bullet though. You still need an appropriate calorie deficit to drive weight loss. Protein should stay moderate to support muscle retention, and fat intake increased to control hunger. Pair carb reduction with whole foods nutrition, activity, and healthy lifestyle habits for optimal and lasting success.