Eating only one meal a day, also known as intermittent fasting, has become an increasingly popular diet and lifestyle trend. Proponents claim it can help with weight loss, boost energy levels, improve focus and concentration, and provide various other health benefits.
But what really happens to your body when you only eat one meal a day for an extended period of time? Here is an overview of the potential effects:
Week 1
Day 1
On the first day of only eating one meal, you may not notice any significant changes. You’ll likely feel hunger pains and food cravings throughout the day as your body is accustomed to regular meals and snacks. The hunger may be distracting at first.
Without getting calories and nutrients from regular meals, your blood sugar levels may drop and you could begin to feel lightheaded, irritable and fatigued. You may also develop a slight headache.
Day 3
By day 3, your body starts to adapt to only getting nutrition during your one meal. You’ll still feel hungry between meals, but the hunger pangs may subside slightly as ghrelin levels decrease. Ghrelin is the hormone that stimulates appetite.
With lower calorie intake, your insulin levels also begin to drop. This allows stored fat to be released and used for energy. You may notice a slight increase in energy despite eating less.
Day 5
At the 5 day mark, ketone production picks up. Ketones are molecules produced by the liver from fat when glucose is scarce. They can be used by the body for fuel. This metabolic shift to using fat and ketones for energy instead of carbs may result in weight loss, improved mental clarity and focus.
However, low insulin can also cause fatigue, nausea, bad breath and headaches in the short term as your body adapts. Be sure to stay hydrated.
Day 7
By day 7, most people report feeling less hungry throughout the day as your body becomes adapted to only eating one meal daily. You may feel an increase in energy and focus. Many people notice they are entering ketosis around this time, which can provide a mental boost.
However, some may struggle with sleep issues during the first week if they eat too close to bedtime. Be sure your one meal is earlier in the day.
Week 2
Day 8
In week 2, the early stages of ketosis have fully set in for most people eating one meal a day. This is when many people report feeling clear-headed, focused and energetic. Hunger cues are much weaker and easier to ignore.
Your body has accessed its fat stores for fuel which may lead to weight loss for some people. For others, fasting this way helps maintain current weight. Both insulin and blood sugar levels remain stable from using fat for energy all day.
Day 10
By day 10, most people experience a stabilization in energy levels throughout the day – no longer feeling starved between meals or hit by the post-meal “food coma.” Your body is keto-adapted.
Some report heightened mental clarity, productivity and mood from ketosis and stable blood sugar levels when fasting this way after over a week. Some may still struggle with sleep issues if eating too close to bedtime.
Day 14
Two weeks in, your body is fully adapted to using fat-based fuel between your one meal a day. Hunger and food cravings are greatly reduced or disappear for most people. Weight loss may occur for those with weight to lose.
Ketone production is at its peak, providing mental focus and feelings of well-being for many on this eating plan. However, be sure to stay hydrated and get enough rest, as fatigue can set in.
Week 3
Day 15
As you enter week 3, you are in full ketosis and likely feeling the benefits like sustained energy, mental clarity and reduced appetite. However, some may struggle with fatigue setting in after 2 weeks of reduced calorie intake.
Be sure to eat plenty of nutritious foods during your one daily meal. Get enough protein, healthy fats and micronutrients like vitamins and minerals. Stay hydrated between meals. Rest as needed.
Day 17
Around day 17, most people report an increase in energy and endurance as their bodies learn to thrive in a fasted, fat-burning state. Ketone production provides steady fuel for both your body and brain.
At this point, many people notice improved body composition and weight loss results as excess fat continues to be burned for energy. Meal planning becomes easier as hunger is minimal between meals.
Day 21
Three weeks in, this way of eating feels completely normal for most people. The body readily adapts to using stored fat for energy throughout the day. Hunger and cravings rarely return between meals.
People report feeling light, energetic, clear-headed and lean at this stage. However, be cautious of under-eating during your one meal. Be sure to get balanced nutrition. Rest as needed between fasting periods.
Week 4
Day 22
As you enter the fourth week, this routine should feel easy physically and mentally. However, some people may struggle with boredom or lack of food variety after 3 weeks of eating the same meals.
Focus on cooking delicious, nutritious single meals with plenty of complexity and variety to keep you satisfied. Social gatherings can also get tricky. Do your best to plan ahead.
Day 25
Around day 25, you may need to switch up your meal plans to allow for more dietary variety while still staying in ketosis. Focus on keto-friendly whole foods. Stay strict about only eating during your meal window.
Some people find they need to take 1-2 days per week to eat more normally and exit ketosis briefly before resuming their fasting routine to stay on track. Listen to your body’s signals.
Day 30
By the end of a full month eating one meal a day, this pattern should feel comfortable and sustainable. However, some may find it difficult long-term without more flexibility on occasion.
Be sure to get blood work done if continuing longer than 30 days. Watch for signs of nutritional deficiencies or malnutrition if not planning meals wisely. Most can sustain this short-term.
Summary
In summary, eating just one meal a day for 30 days forces your body to enter ketosis as it learns to run on fats and ketones between meals. Benefits can include mental clarity, steady energy, reduced hunger and potential weight loss.
But plan your meals wisely, stay hydrated, rest when needed and modify the plan if you struggle. Longer fasting periods may require more flexibility and medical supervision.