DIETS

The low-carb diet

Fewer starches and sugars, more protein, vegetables and healthy fats

Eat plenty of: Non-starchy vegetables, eggs, fish, meat, dairy, nuts
Eat some: Berries, legumes, whole grains in small portions
Eat less: Sugar, bread, pasta, rice, potatoes, sugary drinks
Carbs: Usually under 130 g a day; very low-carb is under 50 g

What it is

A low-carb diet replaces most sugar and starch with protein, vegetables and fats. There’s no single definition: researchers usually call under 130 g of carbohydrate a day low-carb, and under 50 g very low-carb, which becomes the keto diet. Some people simply cut sugar, bread and pasta without counting.

What to eat

Carbohydrates per typical portion, to help you choose.

Food	Carbs per portion	Low-carb?
Leafy greens, broccoli, zucchini	2 to 6 g per cup	Yes, freely
Eggs, meat, fish, cheese	Under 1 g	Yes
Nuts	About 3 to 6 g per handful	Yes, in small amounts
Berries	About 10 to 15 g per cup	In moderation
Lentils and beans	About 20 g per half cup	In small portions
Bread	About 15 g per slice	Limit
Rice and pasta	About 40 to 45 g per cup cooked	Limit
Soda and juice	About 35 g per can or glass	Avoid

A sample day

Low-carb, one day

BreakfastScrambled eggs with spinach and mushrooms
LunchChicken salad with avocado, seeds and olive oil
SnackGreek yogurt with a few berries
DinnerGrilled fish with broccoli and a small portion of lentils

What the research found

Key study

Low-carb and low-fat tied

Randomized trial
609 adults
12 months

Adults with overweight followed a healthy low-carb or a healthy low-fat diet, both focused on whole foods. After a year, the low-carb group had lost 6.0 kg and the low-fat group 5.3 kg on average, a difference too small to matter. Neither genes nor insulin levels predicted who did better on which diet.

Gardner et al. · JAMA · 2018 Source 1

Key study

The same weight lost after two years

Randomized trial
307 adults with obesity
2 years

Both groups lost about 7 kg after two years, with group support. The low-carb group had a larger rise in HDL (“good”) cholesterol, and more side effects such as bad breath, constipation and hair loss in the first months.

Foster et al. · Ann Intern Med · 2010 Source 2

A review of 48 diet trials came to the same conclusion: low-carb and low-fat programs led to similar weight loss at 6 and 12 months ³. In type 2 diabetes, a review of 23 trials found that more people reached remission (blood sugar back below the diabetes range) after 6 months on a low-carb diet, though the advantage was smaller and less certain at 12 months ⁴.

Good for

People who feel fuller with more protein and fat
Cutting sugar and refined snacks
Some people with type 2 diabetes, with their doctor

Watch out for

Missing fiber if you cut whole grains, fruit and legumes
Eating out and social meals are harder
Weight can come back if old habits return
Constipation in the first weeks

How to start

Five first steps

Cut sugary drinks, sweets and white bread first: that alone removes a lot of carbohydrate.
Build each meal around a protein food and two vegetables.
Keep some carbs from legumes, berries and whole grains for fiber.
Use olive oil, nuts and avocado rather than processed meats for fat.
Drink plenty of water, especially in the first week.

Common mistakes

Replacing bread with processed meat and cheese at every meal.
Cutting vegetables along with carbs: most vegetables are very low in carbohydrate.
Eating “low-carb” snack bars and sweets that are high in calories.
Expecting the quick drop of the first week, mostly water, to continue.

With an eating window

Questions

How many carbs a day is low-carb?

Usually under 130 g a day. Under 50 g is very low-carb, or ketogenic. Many people start around 100 g and adjust.

Why do I lose weight so fast in the first week?

Cutting carbs empties your body’s glycogen stores, which hold water. Much of the first week’s loss is water; fat loss is slower and steadier.

Is low-carb better than low-fat?

Not for weight loss over a year or more: in long trials both lead to similar results ^1,2. Choose the one you can keep up.

Sources

Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA. 2018;319(7):667-679. doi.org/10.1001/jama.2018.0245
Foster GD, Wyatt HR, Hill JO, et al. Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet: A Randomized Trial. Ann Intern Med. 2010;153(3):147-157. doi.org/10.7326/0003-4819-153-3-201008030-00005
Johnston BC, Kanters S, Bandayrel K, et al. Comparison of Weight Loss Among Named Diet Programs in Overweight and Obese Adults: A Meta-analysis. JAMA. 2014;312(9):923-933. doi.org/10.1001/jama.2014.10397
Goldenberg JZ, Day A, Brinkworth GD, et al. Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis of published and unpublished randomized trial data. BMJ. 2021;372:m4743. doi.org/10.1136/bmj.m4743

MAKE IT A HABIT

Any diet.
Your eating window.

Fasting Tracker is a free intermittent fasting app for iPhone, iPad and Apple Watch.

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Fasting Tracker on iPhone 18 Pro during a 16:8 fast: Sunny in the middle of the ring, 11 hours 30 minutes elapsed, 71 percent of the goal, a 9-day streak and the current stage, Blood Sugar Falling

dieting.app is general information, not medical advice. If you are pregnant or breastfeeding, have diabetes, kidney disease or a history of eating disorders, or take medication, talk to your doctor before changing how you eat.