Under-Eating and Fat Loss: Signs You Are Not Eating Enough
"I'm barely eating and the scale won't move." If that sounds like your week, the answer I gave on the show has two parts. Living on very low calories for months can slow how much you burn. Eating so little that you cannot stick with it sends you into a weekend binge and a Monday restart. The second one is far more common, and with both I bring calories up first, in steps, before I ask a body to lose fat.
I went through it solo on the Talking Nutrition podcast, episode 212, following on from the episode where I said people diet too much and too often. This post is education and does not replace medical advice.
Can You Be Eating Too Little to Lose Weight?
Yes, in two different ways. I see more people under-eat than overeat, even when fat loss is the goal. That sounds odd, because fat loss is controlled under-eating by definition: fewer calories in than out, so your body uses stored fat. The trouble starts when the deficit gets so deep, or lasts so long, that other things give way.
Scenario one is truly living on low calories for a long stretch, and your metabolism adapts. Scenario two is believing you are on low calories while the plan is so strict that it collapses every few days.
If you would rather hear it in my voice, the full episode is below.
What Does Eating Too Little Do to Your Body Over Time?
Metabolism gets described as fast or slow. The better word is adaptive. Eat a bit more and you burn a bit more, eat a bit less and you burn a bit less, and in a healthy range your body compensates well in both directions.
Stay low long enough and that compensation shows up. I said it on the show and I will say it here: "It's a normal physiological process that is supposed to happen according to your food intake." People talk about metabolic adaptation as a terrible thing, and it is your body doing its job. It also shows up in several places:
Daily movement. "The biggest form of metabolic adaptation, in terms of burning calories, is going to be your NEAT." That is the walking, talking and fidgeting that happens outside the gym, and it drifts down quietly. It is why I have clients track steps in a fat loss phase.
Training. Exercise is only about 5 percent of what you burn per day, and with less fuel you push a little less and burn a little less in the session.
Digestion. Digesting food burns about 10 percent of your day, on average more than exercise does. Less food in means less to digest. My post on what TDEE is shows how these pieces add up.
Muscle. Very low calories raise the risk of losing muscle, and muscle burns more at rest than fat does. My post on how to maintain muscle while cutting covers that side.
Hormones. Thyroid hormone acts in nearly every process in the body, and in some people its output can come down on low intake. In some women a cycle can go quiet or disappear after a long stretch of very low intake. That one deserves a conversation with your doctor.
How do you reverse this? You eat enough. You eat enough, that's it.
Now the correction. I opened the show with this and it is the less common story. After years of coaching hundreds of people, the clients with a truly pronounced adaptation were very few.
Why Does Eating Too Little Lead to Binges and the Monday Restart?
This is scenario two, the common one. Evening cravings arrive and a whole bag of chocolate disappears. The week goes well, then Friday goes sideways, and the thought arrives: "Well, I messed up already, so on Saturday I might as well just keep going." Sunday feels awful, and Monday is a fresh start.
We're eating so little that it's impossible to stick with your diet.
That is a plan problem, and the plan came from an industry that sells aggressive cuts.
By the end of the first quarter most new year's resolutions are finished, because they ask for everything at once: slash the calories, cut the sweets, quit alcohol, 10,000 steps, cardio daily. "No one can live like that."
I know because I did it. Around 2012 I was 30 kilos overweight. I watched a documentary on juice fasting, bought a blender and lived on green juices. I lasted days, hungry and drained, and at the first weekend show with my band I went overboard. Then a calorie app asked how fast I wanted to lose weight and offered a slider. I picked the maximum. "It gave me 1200 calories for a 115 kilo dude. That's way too little." I fell off in no time. If this is you, I'm also not judging, because I made those mistakes myself.
Most under-eaters have never seen their maintenance number.
The calculator gives you your maintenance calories and a starting point for a sane deficit, so your next plan starts from a figure and stops being a guess.
Use the free TDEE calculator →
What Are the Signs You Are Not Eating Enough?
None of these diagnoses anything, and each has other possible causes. Together they form the picture I look for with under-eating:
Evening cravings strong enough to clear a whole bag of chocolate.
Good weekdays followed by a Friday or Saturday that collapses.
Feeling hungry and drained through most of the day.
Steps and general movement sliding without you deciding it.
Training sessions that feel flat, with less push than you used to have.
A cycle that changes or goes missing, in some women, which belongs with your doctor.
Scale weight racing down well beyond the first couple of weeks, which can mean muscle is leaving along with fat.
That last one surprises people, because the complaint was a stuck scale. The first couple of weeks include glycogen and water, so quick early numbers can be normal. If the drop keeps racing, I slow it down on purpose.
How Does Eating More Fit Into Fat Loss?
One client came to me eating somewhere around 1,600 to 1,700 calories, as I remember it, with a lot of steps and workouts on top. I raised her through 1,800 and 1,900 to 2,000. She started losing too fast, so I slowed her down, because I did not want her losing muscle. She stayed around 2,000 for the rest of her fat loss phase and lost about 15 percent of her body weight in total. That is one client with her own activity and history, and nothing in it is a promise for you.
The point of all that is the deficit, so here is what I said on the show:
I want you to lose body fat at as many calories as possible.
I start people around a 20 percent deficit and skip the slash down to 1,200. That leaves room for filling foods, hunger stays lower and the evening cravings fade.
A deficit followed by a weekend of overeating averages out as maintenance, while a moderate one you can hold all seven days gives the scale something to respond to. The pace I aim for is 0.5 to 1 percent of body weight per week, and 1.5 now and then is fine.
Tracking makes this visible. My clients learn it in about five minutes a day, and my post on tracking macros for beginners covers the setup.
What Do I Do With a Client Who Has Been Under-Eating?
Maintenance first. A client of mine lost 10 kilos in her first fat loss phase and has about another 10 to go. We moved her to three months of maintenance, and it scared her. She worried the scale would climb, and eating more felt uncomfortable. If a rising number is your fear too, my post on weight fluctuations explains why a few days of movement on the scale can be normal.
I educated her on metabolism, and I was honest that explaining only goes so far. The only way it clicks is doing it, so we run a reverse diet, our method of bringing calories up step by step, with the right foods in the right amounts, alongside good training. I told her I would keep things in check, and the plan was to hold the 10 kilos while her metabolism picked back up.
I map the whole year for her: a fat loss phase, a break, a second phase later. With 20 or 30 kilos or more to lose, that takes time, and I am comfortable with that. My rule of thumb is a maintenance block of two thirds up to one times the length of the deficit. With more than 10 kilos to lose I park muscle gain and maintain for now, and body recomposition waits its turn.
Where Should You Start This Week?
Ask yourself which story is yours. Have you truly lived on low calories, or have you followed a strict diet, fallen off, overeaten and restarted? In both cases I go maintenance first, build the habits, then run a fat loss phase of maybe three months, then reverse diet back up in a couple of steps.
I said it near the end of the show: "Don't stay in low calories. You gotta have those breaks."
The episode runs 21 minutes and holds more of the story than fits here.
Find the number before you change the plan.
Put in your stats and your real activity level and you get maintenance calories plus a deficit worth starting from. Bring that figure to your next week of meals.
Use the free TDEE calculator →
Written by Johan Vesters, functional health and nutrition coach (FNMS, HMCC L1, MMU L1, PN1, CFL1, NCI L1) and founder of Odyssey Coaching Systems.