Someone asked me a cool question about “what happens after a diet?” The concern was about increasing calories and whether this simply results in regaining weight once you stop being in a calorie deficit.

The short answer is no. The calorie deficit is required to bring about weight loss, but it is not required to maintain a healthy weight. In fact, quite the opposite. While a calorie deficit can have health benefits if it results in a healthier body weight, there is little else “healthy” about the process. We should not be aspiring to be under-fuelling or malnourishing our bodies for extended periods of time unless medically advised to lose weight.

Following successful weight loss, the goal should shift from eating to lose weight, to eating to maintain body weight. Depending on how aggressive your dieting has been, your maintenance calorie intake could be anywhere in the region 200-500kcal+ higher than your current calorie intake.

However, there are a huge number of variables that can complicate this picture. It’s very possible your maintenance calorie intake following weight loss is significantly lower than it was before your weight loss. There’s a few reasons for this.

Primarily, if you’ve lost considerable amounts of weight, your resting metabolic rate will now be lower, as you have less active tissue requiring an energy supply. (Smaller bodies require less energy)

Secondly, if you’ve been dieting for a considerable time frame, and have lost a considerable amount of weight, you may also have experienced a degree of decreasing energy output. This may be something obvious like feeling too tired to go on your usual runs now that you’re eating less, or skipping a few gym session through fatigue.

It could also be from less obvious avenues, like a down regulation of non-exercise activity thermogenesis (NEAT - basically all your subconscious movements, fidgeting, standing, hand movements, pacing etc.) There may even have been a degree of adaptive thermogenesis, which essentially involves a slight decrease in RMR as your body has begun to slow down some processes to mitigate the lack of energy coming in, in an effort to slow weight loss. (1)

Both the slow down in NEAT and possible decreases in RMR are physiological responses to dieting that effect the output of energy. Interestingly though, towards the later stages of a weight loss “phase” increases in appetite can also lead to subconscious eating and underreporting calorie intakes. The combination of decreased output and increased input can cause a plateau in weight loss. This is because by this stage, calorie intake has crept up a little more than we think, and calorie output had crept down more than we think (2). If you’re “finishing your diet” because you’ve hit a plateau, one way or another you’ve already arrived at maintenance calorie intake and are no longer in a deficit. (This is also probably a good sign you may need a break from dieting!)

More confusingly, on the other end of the spectrum, it is also possible that following weight loss your maintenance intake may now need to be HIGHER than it was prior to weight loss once you start to eat normally again! If throughout your weight loss journey you’ve now started walking to work everyday and training 5 times a week (where you weren’t before) you may find that you maintain weight at a higher calorie intake than you did previously, simply because your energy expenditure is now much higher.

In a nutshell, as we arrive at the end of a “diet phase” it’s really difficult to actually know how many calories we’re truly expending each day, how many calories we’re really consuming each day, or exactly the rate at which our energy output is likely to increase as we increase our energy intake. Because of this, sticking some numbers in a calorie calculator and hoping it will give you an accurate maintenance figure is perhaps not the best approach to go for.

A more sensible approach is to slowly introduce more calories to the diet. Start by adding 100kcal each week to your daily intake and monitor how you’re feeling. It’s normal for the scale weight to go up slightly in this process as you’re likely to be physically fuller with food, replenishing depleted glycogen stores and retaining more water. Don’t worry about this. As you increase your calories you should notice a corresponding increase in your energy levels and thus energy expenditure. Keep an eye on the scale and how you feel in yourself across this time. Barring perhaps an initial gain of a few pounds, if throughout this time your weight remains stable you may wish to keep your intake about the same, or even look to increase it slightly. If you do see a slow trend towards weight gain over weeks and months, perhaps scale the calories back slightly or look to increase activity.

We can talk to death about calorie math but ultimately our ability to truly know for sure how many calories are going in (at the point of substrate absorption/utilisation) and are going out (through a variety of responsive output channels) is incredibly limited! The only real way to find out is by increasing the calories slowly and sensibly and seeing how you respond. Nothing drastic happens over night. Weight loss requires a considered, consistent trend towards a calorie deficit over weeks, months and years. Weight gain requires a considered, consistent trend towards a calorie surplus over weeks, months and years. Maintenance calorie intake is a broader range than we typically think, our body regulates inputs and outputs very well to help us maintain our weight.

Talking about “Calorie deficits” is all the rage at the moment and yes they are essential for weight loss. However, they are not something that is required to MAINTAIN a lean and healthy physique.

1) Rosenbaum & Leibel (2010) “Adaptive Thermogenesis in Humans”

2) Polidori et al. (2016) “How strongly does appetite counter weight loss'“