Diets suck! That’s a fact, and not only are they no fun, they don’t even work! Sure, people lose weight on a diet, I’m not disputing that. The problem is that virtually everyone puts that weight back on, and in many cases they put back on more weight than they lost in the first place, and end up with even worse associated health problems than before such as diabetes, skin, cholesterol and heart problems as well as other metabolic issues.
The studies show that 80% of people who lose more than 10% of their body weight on a diet will have put that weight back on within a year, and one third to one half will have put more back on than they originally lost (1). What is more shocking is that each subsequent time a person goes through the cycle of weight loss then regain, often called ‘yo-yo dieting’, the amount of weight regain grows, and the associated health problems such as high blood pressure, high cholesterol and high blood sugar also get more serious (2,3).
However, a new study has finally shed some light on why this cycle happens so often. It also tells us the real secret to losing weight, and then keeping that weight off as well as keeping the other positive changes weight loss brings to our health permanently.
The study published last week in the journal Nature looked at ‘Yo-Yo Dieting’ in mice, scientifically known as ‘weight cycling’. The researchers cycled the mice by feeding them unhealthy and then healthy diets to manipulate their weight between normal and obese. They then carefully measured all of their physiological responses and compared them against controls (mice that hadn’t gone through the weight cycling process).
They found that with each subsequent ‘cycle’ the mice got fatter than before, they also had worse blood sugar levels, higher levels of LDL (the bad cholesterol), were less active despite having the same amount of food as their control counterparts, and had higher levels of the hormone leptin (5).
Leptin is the body’s ‘starvation hormone’ and also our ‘master hormone’. Discovered in 1996, it’s produced by the body’s fat cells, but is still not widely known outside the scientific community. When our fat stores are low, leptin levels are also low and the brain receives the signal to turn down energy burning, making us less energetic, allowing us to store more fat. However, as fat stores rise, leptin levels increase and signal the brain to produce more energy, making us more active so we can reduce fat stores. However, with each yo-yo dieting cycle our brain becomes resistant to the signal of leptin, so even when our fat stores are full and leptin levels our high, our brain doesn’t understand it and energy burning is turned down.
Basically our brains become switched off to the signal of leptin during periods when it’s level’s are chronically high, and we become ‘leptin resistant’. Even when our fat cells are producing more and more we don’t produce any more energy, or become more active. It’s a vicious cycle and because it’s our master hormone, when leptin levels are pushed too high, other hormones can be adversely affected and be either increased or decreased to a level where they are out of balance, potentially causing metabolic problems throughout the body.
The good news is that these problems only surface when the mice were obese or becoming obese. As soon as they lost weight in a dieting cycle all their physiological problems went back to normal, so no high cholesterol, blood pressure, leptin resistance and blood sugar problems. Energy levels went back to normal, as did food intake. The problem is of course staying slim, and the question is why do people slip back into a weight gain cycle if all the physiological problems of the body have returned normal?
The researchers found the answer when they tested the gut bacteria of the mice. They found that even when the mice ate a healthy diet that led to their weight becoming normal again, as well as all the other physiological problems associated with obesity going back to normal, their gut bacteria would continue to be ‘abnormal’ for a considerable length of time.
We’ve covered whether your gut bacteria can make you fat in another blog post here. You gut bacteria can affect every physiological process in the body from the action of leptin, to cholesterol levels and how much energy we burn. The fact that bacteria levels remain altered for a considerable amount of time after weight is lost is really a key finding. The researchers found that is could take up to 21 weeks for the microbiome (i.e their gut bacteria) of the mice to return to the same makeup as normal mice who had never been obese and eaten unhealthily. This 21 week period was 5 times longer than the weight gain or dieting period.
The researchers went on to test whether the microbiome was responsible for faster weight regain further by giving obese mice antibiotics to knock out the bad bacteria that populated their guts during times of eating unhealthily and becoming obese. Amazingly the mice receiving antibiotics did not become as fat, or develop as serious other health issues when they re-fed unhealthy diets, as mice that were not given antibiotics.
The researchers then went a step further, however, this time instead of using antibiotics to kill the ‘bad’ bacteria they used fecal transplants (literally poop transplants) from healthy non obese mice, and transplanted them into the mice that had never been been through several dieting cycles.
These fecal transplants changed the gut microbiome of the obese cycling mice to one similar to the healthy mice, and when that happened the mice no longer gained weight at the same rate, or developed other problems like resistance to leptin and high cholesterol.
The Secret to Maintaining a Healthy Weight Long Term
Although Fecal transplants have started to become available for treatment in people, they are still very much in the early stages of development, and lot’s of people just plain don’t like the idea. Also indiscriminate antibiotic use can also cause problems by killing beneficial bacteria as well as bad bacteria.
The good news is that we don’t have to follow either of these routes, there are basic common sense steps we can take to reach and maintain healthy weight levels that don’t include starving ourselves or looking for the latest new diet fad.
The only problem is that it’s not quick or ‘sexy’. The only reliable way to lose weight long term, and keep it off is to eat healthily without starving yourself. That means eating real food, and cutting out processed foods, refined carbohydrates and sugar. You don’t diet, you just have to permanently eat healthily, in a way that can always be sustained permanently.
You don’t have to cut calories below normal levels, because every time someone does that they eventually break. There may initially be problems with cravings for sweet and bad foods, but these pass with time, and they are much more bearable when calories are not being restricted. The longer we spend without processed food the more our hormones balance, and the less cravings we get.
We also need to work on our guts. That means adding fermented foods and drinks to our diets (choose ones you like!) such as sauerkraut, Kefir or Kombucha (Kombucha is my personal favourite), as well as adding a good probiotic daily, and ensure you get plenty of fiber in your diet, which acts as food for you gut bacteria (known as prebiotics).
The next thing is to make sure you get physical activity regularly, but you must choose something you enjoy, that you will keep doing long term. If you don’t enjoy it, it’s just another ‘yo-yo’ activity which will be given up at some point.
Finally, we have to keep going. It took up to 21 weeks to normalize gut bacteria after weight loss on average in mice, this period could be much longer in humans and possibly take several years, and there will definitely be plateaus along the way. However, as long as you are eating good quality tasty food, looking after your gut with drinks or food you like, enjoying the occasional treat, and doing physical activity that brings you pleasure, what’s the rush?
(1) Dulloo, A. G. & Montani, J. P. Pathways from dieting to weight regain, to obesity and to the metabolic syndrome: an overview. Obes Rev 16 Suppl 1, 1–6, doi:10.1111/obr.12250 (2015).
(2) Pietilainen, K. H., Saarni, S. E., Kaprio, J. & Rissanen, A. Does dieting make you fat? A twin study. Int J Obes (Lond) 36, 456–464, doi:10.1038/ijo.2011.160 (2012).
(3) Montani, J. P., Schutz, Y. & Dulloo, A. G. Dieting and weight cycling as risk factors for cardiometabolic diseases: who is really at risk? Obes Rev16 Suppl 1, 7–18, doi:10.1111/obr.12251 (2015).
(4) Anastasiou, C. A., Karfopoulou, E. & Yannakoulia, M. Weight regaining: From statistics and behaviors to physiology and metabolism. Metabolism 64, 1395–1407, doi:10.1016/j.metabol.2015.08.006 (2015).