Many people who find themselves eating a ketogenic diet do so because they want to shed excess body fat. If you read my Keto Basics series, then you are familiar with the benefits of a ketogenic diet and these reasons may also be what helped you to find ketogenic nutrition. (If you have not, I highly suggest you start at the beginning so this all makes sense to you.) For most of us, however, the lure of a keto diet is quick and easy weight loss.
When it comes to mobilizing our body fat stores (what most people call “weight loss,”), a keto diet offers a few benefits that do, in fact, make this process easier than eating a high carbohydrate diet. Ketosis helps to stabilize blood glucose levels and satisfy a person’s hunger, which helps to naturally regulate caloric intake (Dashti et al., 2004).
When our energy is stable, our hunger is stable. This makes it easier to go for longer periods of time without snacking and also makes overeating hard to do. Thus, eating for body fat loss, or dieting, is made easy by a ketogenic diet.
However, there is a such thing as a right way and a wrong way to diet. In various Facebook groups, message boards and even among my clients, I see how hard many of you are working to lose body fat, get into shape and heal your bodies. Unfortunately, old dieting mentalities of cutting calories low are hard to reverse. I often see that someone is eating 1,200 calories and going to the gym every day running on a treadmill, taking an aerobics class or doing some other form of chronic cardio in an attempt to reduce body fat. These strategies may work temporarily, but within a couple of weeks, people often find their weight stabilizes and despite eating at a severe caloric deficit, they simply cannot shed body fat.
So what do most people do when fat loss slows down or stops on a calorie-restricted diet? They restrict calories further, of course, and repeat the next time a stall occurs. This pattern is bad, bad news. Severe calorie restriction is the wrong way to diet.
So let’s clear up some truths and myths about calorie restriction.
- Do you have to eat at a deficit in order to drop body fat? Yes. But without sophisticated measuring equipment, it is nearly impossible to know exactly how many calories you burn day to day. Your daily metabolism varies based on a number of factors that change too frequently to be measured concretely. In addition, if you are in ketosis, your metabolism runs faster and more efficiently than if you were glucose fueled. Thus, you burn 200-300 more calories just for being in ketosis. You are already in a deficit even if nothing else changes except replacing carbs with fat. (see Kennedy et al., 2007 and Seaton et al., 1986 for details). Because a ketogenic diet is thermogenic, or fat burning, calculating a person’s actual daily energy expenditure while in ketosis is very difficult. The calculators that apply to a glucose burning metabolism do not directly apply when because ketosis changes the base metabolism (Kennedy et al., 2007 and Seaton et al., 1986).
- Do you have to starve yourself to drop body fat? No. Eating 300-700 calories fewer than you burn is enough to help you mobilize over a pound a week of body fat. One study that compared low fat and low carb protocols put people onto diets for fat loss (Greene et al., 2003 and Greene, Devecis and Willet, 2004). There were three groups in total. One group was given a low fat (LF) diet and a second low carb (LC1), and members of both groups ate a total of 1500 calories a day for women and 1800 calories a day for men. A third group, also low carb (LC2), was allowed 300 additional calories a day (1800 calories for women and 2100 calories for men). All three groups lost fat, but both the low carb groups lost more fat than the low fat group (LC 1: -23 lbs, LC 2: -20 lbs, and LF: -17 lbs). While the low carb group that ate at a deficit lost the most body fat, both the low carb groups lost more fat than the group that ate a higher carb and lower dietary fat. Eating at a large deficit is not necessary for fat loss. Eating at a deficit at all is not even necessary.
- Does eating at a large deficit guarantee faster weight loss? For a while, it will. You can eat rice cakes and Snickers all day and drop massive amounts of weight if eating at a big enough deficit. And eating at a large deficit does not guarantee fat loss but weight loss? The difference? Fat loss means loss of body fat and weight loss can include losing fat and muscle, which is more bad, bad news. If you eat at a large deficit, over time the body catches on to the fact that it is burning far more energy than it is taking in and it stops burning as much. This is how body weight can stabilize even when eating very low calorie (1,200 calories is low). It is even possible to gain body fat eating this little.
- Does eating at a large deficit slow the metabolism? Y E S. This is what happens when you cut calories low and then notice that your fat loss stalls. Weight loss is not linear: many people gain muscle while losing fat and show no changes on the scale. But very commonly, the body catches on to the fact that it’s been burning 2,000 calories of energy and only taking in 1,200 calories. Eating that little must mean that you are in a famine—otherwise, why else would you be eating so little? (And if you are exercising on top of this, it’s even worse). So the body cuts non-essential functions to slow the rate at which you use body fat for fuel until you can replenish your stores. Namely, it slows your thyroid, which happens commonly on diets: you get cold, your hair falls out, your skin gets dry, you become moody/anxious, your sleep becomes disrupted, your brain gets foggy and does not work as well, you lose muscle, etc. All of these are also signs of actual starvation, but dieting (eating too low calorie) can create these symptoms too. For more information on this topic, see this recent post.
So how should you eat if you want to lose body fat?
- Determine your estimated TDEE as a starting point. If you have no idea how many calories it takes to maintain your current weight (total daily energy expenditure or TDEE), then try a calculator for TDEE so you have a starting point for estimating your current energy needs: https://ketodietapp.com/Blog/page/KetoDiet-Buddy. Be honest about your weight, your body fat and your activity level. People often underestimate their activity and end up under eating because they were not honest in this step.
- Determine the macros that work best for you. A keto calculator can help you work out how much to eat, but what’s critical is not to let your fat calories get more than 300-700 calories under your TDEE. This is the deficit window I recommend. It works well to mobilize fat stores and also prevent the metabolism from slowing down.
- Once you figure out your deficit, eat this way for up to a week and then spike your fat calories for a couple days so your metabolism does not slow down. Alternating high and low calories is a great way to trick the body into burning calories at the higher level. For example, if you eat at a 700 calorie deficit, I would spike calories by this amount (yes, 700 calories!) every 3-4 days. If you eat at a 300 calorie deficit, I would spike calories by this amount once a week.
If you have success using this strategy for weight loss, please comment below. I would love to feature your experience in an upcoming blog post. Thanks for reading!
Dashti, H. M., Mathew, T. C., Hussein, T., Asfar, S. K., Behbahani, A., Khoursheed, M. A., … Al-Zaid, N. S. (2004). Long-term effects of a ketogenic diet in obese patients. Experimental & Clinical Cardiology, 9(3), 200–205. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2716748/.
Greene, P., Willett, W., Devecis, J., et al., “Pilot 12-Week Feeding Weight-Loss Comparison: Low-Fat vs Low-Carbohydrate (Ketogenic) Diets,” Abstract Presented at The North American Association for the Study of Obesity Annual Meeting 2003, Obesity Research, 11S, 2003, page 95OR.
Greene, P.J., Devecis, J., Willett, W.C., “Effects of Low-Fat Vs Ultra-Low-Carbohydrate Weight-Loss Diets: A 12-Week Pilot Feeding Study,” abstract presented at Nutrition Week 2004, February 9-12, 2004, in Las Vegas, Nevada.
Kennedy, A. R., Pissios, P., Otu, H., Xue, B., Asakura, K., Furukawa, N., Marino, F. E., Liu, F.-F., Kahn, B. B., Libermann, T. A., and Maratos-Flier, E. (2007). A high-fat, ketogenic diet induces a unique metabolic state in mice. American Journal of Physiology – Endocrinology and Metabolism, 292(6):E1724-E1739. http://ajpendo.physiology.org/content/292/6/E1724.full…
Seaton, T. B., Welle, S. L., Warenko, M. K., and Campbell, R. G. (1986). Thermic effect of medium-chain and long-chain triglycerides in man. The American Journal of Clinical Nutrition, 44(5):630–634. http://ajcn.nutrition.org/content/44/5/630.short
Total daily energy expenditure calculator: https://tdeecalculator.net/