What Is "Starvation Mode"?
As a natural physiological and biochemical response to deep caloric restriction, your body will slow its metabolism in an attempt to keep you from dying. This essentially means slowing down the rate in which you burn calories, as well as making you feel lethargic to keep you from moving around too much. You'll also have a deeper yearning for food, since your brain is telling your body that you absolutely need to eat.
- Metabolic slowing with massive weight loss despite preservation of fat-free mass: https://www.ncbi.nlm.nih.gov/pubmed/22535969
A more technical term for "starvation mode" is adaptive thermogenesis.
- Adaptive thermogenesis in humans: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/
What starvation mode actually is and what a large amount of people think it is are two different things.
What Starvation Mode Is Not
What people think starvation mode is:
If you restrict your calories too much, your body will stop burning fat completely and you'll even gain weight. To prevent this from happening, you need to eat more calories so your body knows it has enough to survive.
This is very far from the truth, and it's very misleading to those that want to start a fat loss journey. Using the logic above, one might assume that they need to simply eat a little less than what they have been (despite never tracking how much they eat) and all is well. If they don't see their weight go down, they are officially in starvation mode and must eat more to compensate.
It's a vicious, illogical cycle.
Calories In vs. Calories Out
One thing we must understand is one pure fact that never fails: expending more energy (calories) than we take in (eat) will result in fat loss.
While adaptive thermogenesis indeed does slow down one's metabolism, it does not mean you will completely stop losing fat. If you weighed 260 lbs (118 kg) and lost 60 lbs (27 kg) over the course of a few months and noticed you're no longer losing fat: this does not mean your body is in starvation mode.
What it means is that you need to adjust your calories again. What you ate during the first 60 lb loss was enough to keep you losing weight, but now you're 60 lbs lighter. Which means you require less calories to sustain the 200 lbs you're currently at than you did at 260 lbs. You can do that by expending more energy through working out, or eating less (or both).
You Can Burn Calories Differently from One Day to the Next
While calories in vs. calories out always remains true, there's some reasoning behind the fact that a person may be seeing slower weight loss than they previously were.
- BMR: Basal Metabolic Rate
- TEF: Thermic Effect of Food
- Physical activity (EAT and NEAT)
As you're losing weight, these three things lessen as well, lowering your overall TEE. (Source)
- Changes in energy expenditure resulting from altered body weight: https://www.ncbi.nlm.nih.gov/pubmed/7632212
Think about it this way: if you've already lost 30 lbs and only want to lose 15 more, you've already accomplished 66% of your goal.
- You have less weight to carry around when you're moving and exercising, and even sitting around (EAT and NEAT).
- You're eating less food due to your caloric restriction, so you also burn less through TEF.
It only makes sense that the closer you get to your goal, the more difficult it will become.
Metabolic Slowdown Is Unavoidable, But Can Be Mitigated
Because of adaptive thermogenesis, metabolism is going to slow when you're losing weight. There are, however, some things you can do to help keep it in check and reduce your chances of losing muscle mass.
Lifting weights has shown that people can keep catabolism of muscle down.
- Resistance training conserves fat-free mass and resting energy expenditure following weight loss: https://www.ncbi.nlm.nih.gov/pubmed/18356845
In the study, the women that did resistance training kept their fat-free mass (FFM) and resting energy expenditure (REE, but essentially interchangeable with BMR (source)).
Up Your Protein Intake
Macronutrient ratios are always highly debated, but one thing that shouldn't be: if you want to lose less muscle during a cut or weight loss routine, increase your protein intake. High protein diets can help curb cravings and maintains your total energy expenditure.
- Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women: https://www.ncbi.nlm.nih.gov/pubmed/11838888
- Maintenance of energy expenditure on high-protein vs. high-carbohydrate diets at a constant body weight may prevent a positive energy balance: https://www.ncbi.nlm.nih.gov/pubmed/25466951
Refeeding During Your Diet
There are a lot of methods of refeeding. Some may recommend that you have a refeed day once every two weeks, some may recommend eating just above maintenance calories for a few days every few weeks. Whatever you choose to do, a refeed can be helpful to maintain both your state of mind and your hormonal balance
As long as you don't turn refeeds into overindulgence, you'll still be on track with your weight loss journey. You may gain extra water weight or a pound or so, but the mental and physical benefits may very well outweigh the slightly prolonged journey.
Starvation mode isn't as dire as many people seem to make it out to be. It's real, but if you go into your weight loss with the knowledge above, you don't need to psyche yourself out and think you're stuck in a rut.
Keep at it, keep consistent, and don't give up. We've got your back.
P.S. Let's just called it adaptive thermogenesis, huh? The term "starvation mode" irks me. You're not starving, you're alright!