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Benefits & Side Effects

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Following on from the NHS article on IF and their weak list of side effects I think it would be useful to have a thread that lists IF practitioners negative experiences.

Before stating any side effects it’s worth providing a bit of detail on what IF entails for you. As you can see from my profile details on the left I have been IFing since late august last year. I 5:2 and throw in the odd day where I refrain from eating anything between b’fast and dinner. After 10 weeks or so I changed my fast days into pure fasting so ate nothing from b’fast thru till b’fast the next day. On most fast days I manage to get in an hour of road cycling or swimming and exercise regularly on non fast days too.

My list of negative side effects/experiences are:

Feeling cold Not surprisingly the winter has really exacerbated this and I now no longer fast for a full 24hrs on fast days, instead have a couple of bowls of veg soup in the evening to help combat the cold.

Irritable/snappy Experience this sometimes on the evening of a fast day.

Cramp Have experienced this some nights after fasting and exercising. Can remedy by eating a little table salt, if I remember.

Dizziness Have experienced this a few times this side of xmas, when standing up after sitting. I presume it’s linked to low blood pressure.

Decline in enjoyment of exercise Many people say that they have no problem exercising with fasting. Not so for me, I find it noticeably harder, but still doable. Over xmas I ate normally (excessively) for 10 days and noticed a real positive difference in the way I felt when exercising both on longish bike rides and when doing sprints in the pool.

Overcompensate on confectionary on feed days I don’t keep a food diary of what I consume but my feeling is that I over compensate on choc, biscuits, ice cream on feed days. This may also be more noticeable now that we are in the middle of winter, so SAD influence creeps in?

Increased bilirubin count My bilirubin count has always been high, circa 30umol/L. After 10 weeks or so of IF and after fasting for 24 hrs I had a blood test and bilirubin count clocked in at 77umol/L. This has no perceivable effect on my everyday living but I think is an interesting observation.

I hope this all doesn't read as being too negative. I still believe that it's worth continuing with 5:2ing. ;)
I am fasting on a Monday and a Thursday and fast for 24 hr then eat 500 calories. I also run about 5 times a week, usually between 5-7k, so about 30-45 mins joogging.

I haven't noticed much of a difference since starting 5:2 on 2nd Jan 2013. I got a really sore head on my 4th fast. I have felt a bit light headed a few times during fast day but that's about it.

I have felt fine exercising too. I have only run on one fast day so far but didn't find it any more of a struggle.

Thankfully I have no bad breath or gastric problems for me.
What a great idea for a topic!

I've been doing 5:2 since August, I started on lunch & dinner of 250cals but this made me extra hungry so after 6-8 weeks doing that I swapped onto a 400-500 cal dinner, sometimes allowing myself 50 cals of that to have a low cal soup or hot choc during the day if needed. I fast on Mondays & Thursdays. I try not to eat after dinner on the day before a fast day, but that isn't always adhered to ;)

The only side effects I've had have been:

Feeling cold Worse since now it's winter, and moreso too when it's 'that time of the month'.

Irritable/snappy Definately less patient with my husband when he gets home from work an hour or two before dinner! I work from home all day so am on my own and don't know if I'd be snappy the rest of the time too. I don't seem to get snappy with anyone else I encounter in the daytime - delivery folks or people in the local shop.

Loss of concentration For most of the day I feel really alert and quite chipper! About 4pm I notice a slight decline in my concentration, but perk up again within an hour and can happy carry on through until dinner at about 6.30pm. Actually this might not be specific to fast days, I'm probably just more aware of it then due to the hightened alertness for the rest of the day. I think a lot of us start to wain towards the end of work anyway!

Overcompensate on confectionary on feed days Same as above, I've found myself overcompensating in the last month but only the day immediately after the fast (Tues/Fridays). The other days I eat pretty normally. I know I'm more inclined towards snacking in cold weather and usually a chilly piece of fruit doesn't cut it for me then, I just want some comfort food! I think I'd be just as bad fasting or not ;)

Do we also have a thread for positive side effects? If there isn, I'll go reply now. If not, I shall make one!
Great topic.

I also fast on Mondays and Thursdays. I fast from 6pm the night before until 11am on the fast day. I then eat 250 cals and then 250 cals at 4 or 5pm that evening (trying to make it longer).

I am dizzy sometimes, I have the odd headache, I walk 6 miles a day without a problem, even on fast days. I feel grumpy early evening until I've eaten, then I feel fine. I don't have bad breath or gastric problems. I am colder. I have over-compensated on some feed days, but I have always been a binger. I am tackling this as a seperate issue and I hope to win, because it is a fight, one I have been fighting for over 20 years. I'm 44.

I feel bloody marvellous :D. 7lb gone, never to return.

Michelle x
The only side effect I've really noticed is feeling the cold more on fast days. Even on the weeks where I've thought that I might have overcompensated on feed days I've lost weight...
I am sure that I am a bit more grumpy on fast days, but nothing too bad.

I did try back to back fasting days on one occasion and felt a bit lightheaded towards the end of the second day.

Otherwise the main negative side effect is feeling hungry on fast days!
I have been following this diet since August, I follow the model Dr M used in the Horizon program, EG I energy restrict to a maximum of 600 calories within 24 hours 2 days a week. 24 Hours for me is when I wake up (6:30am) till I wake up the next day. I eat breakfast, lunch and dinner, usually split at 200, 25-50 and 300ish.

Side effects I have noticed are:

Feeling cold I do feel the cold more than before I started this diet, I guess after losing 2St I am just not as well insulated as I was :roll:

Irritable/snappy I did used to get a bit short with people on and just after fast days, but I don’t think I get as bad now, at least I feel ok.

Loss of concentration Again I did struggle a bit with this, but now I feel sharper on fast days.

Overcompensate on confectionary on feed days Not been a problem for me at all. In fact I have to make an effort to keep my intake up on feed days to stop losing weight.

Bad breath My wife did tell me this has been a problem, but mouth rinse, brush etc helped.

Exercise Exercise has not been a problem, but hard work has. I have felt faint after doing a proper days work. I have a fairly sedentary job driving from place to place where I get in and out a car about half the day, the remainder is spent in the office. I have wondered how someone with a very physical manual job (Bricklayer, etc) would cope with this diet. I suspect if your job is that physical you probably don’t need to follow this diet in the first place or certainly not to lose weight, but I don’t think I could cope with very hard physical job and only eat 600 calories in 24 hrs.

Constipation This has been a problem and continues to be albeit to a lesser extent. this is definallty linked to this diet for me, I never had any problems before starting.
Only fasted one time so far but here's a new negative - bad dreams. No, I wasn't being chased by a giant doughnut but weird, unsettling dreams and poor sleep.

Another possible drawback is rambling on to my friends and family about the 5:2 diet and how they should all try it. They must be getting tired of it .. ;)
haha, i think a lot of us find ourselves going on about this lifestyle!

as for the bad dreams, perhaps that was just coincidental - if i were you I'd do a few more fasts before judging that as a side effect.
i find things like cheese or bananas give me weird dreams regardless of whether I've fasted or not. that pre-dates me starting 5:2.
Hi Moogie

Yes maybe the bad dream thing was a coincidence. I'm fasting today so it will be interesting to see how I sleep tonight.

I'm prone to sleep problems so the fasting might well have nothing to do with it.

So far, I'm experiencing many more positives than negatives, mainly increased energy and positivity which is fantastic :) . I think it's important to stress this to anyone reading and considering a first fast.
OK so, I am fasting two days a week. I eat normally on day 1 (not necessarily forgoing a snack in the late evening), I don't eat anything on day 2 until the early evening when I have my 500 cals, I don't eat again until I wake on day 3. I try to leave at least 2 days between fasts.

Negative experiences
Feeling hungry: I do feel very hungry as it nears the time for my single meal but I think that is just the anticipation of the meal to come rather than real hunger pangs. Mainly the hunger feelings are mild and easily ignored.
Being irritable: I think I may be more irritable towards the time of the evening meal but then I'm often irritable then as I have my son causing me grief with his homework issues then anyway! :roll:
Headaches: I got these at first but don't generally any more unless I fail to drink enough. Oddly I am also less thirsty than I was during the first few week's worth of fasts so I have to remind myself to drink enough.
Feeling cold: this is unsurprising because digesting and processing food generates heat. I try to do a few mins on the exercise bike when I am feeling cold as this not only warms me up but also stops me from feeling hungry.
Bad breath: No-one has mentioned this to me yet, but I'll just nip off and clean my teeth again anyway :D
Overcompensate on confectionary on feed days: Not a problem here. I'm not a big fan of confectionary anyway, but I do like my cake. I sometimes have cake and coffee at 10.30 am and sometimes a dessert after dinner on feed days but not every time and not often both on the same day.
Exercise: Not been a problem but I do minimal exercise anyway :oops:
Constipation: Rather the opposite actually :?
Dizziness/feeling lightheaded: I have been getting this occasionally on feed days rather than fast days and I am wondering if my high blood pressure that is being treated is dropping too low.
Feeling strange on the morning of the first feed day: This is the only side-effect that I haven't seen anyone else mention. My stomach feels odd,sort of sore, and I seem to get full quickly but then feel hungry again soon after eating. I feel like I do when I have had a tummy bug and have recovered to the point where I am not really sure if I am still sick or just hungry (so I am guessing it is something to do with having an empty stomach). I have had this every time so far. It usually fades away by lunchtime. I was wondering if I am having too big a breakfast. I'd be interested if anyone else has experienced this?

Overall, the negative effects have been very minimal and perfectly manageable so far.
Hmmm.... More bad dreams after second day of fasting. But 4 pounds off so still smiling :)
Have only been fasting for two weeks but have noticed feeling cold on fast days. Also suffer from indigestion and heartburn especially the day after fasting. Feel really full very quickly and certainly can't eat as much as I use to before starting this diet. However that must be a positive and I'm sure I will adjust to it. :roll:
I also feel full very quickly the day after fasting and will have to think about a change in my eating habits, ie: eating a substantial lunch or going for lunch is now difficult, breakfast and dinner still fine.

My husband is the same.

Will take a period of adjustment maybe?

Not necessarily a negative, just different!
Find it harder to sleep the night of a fast day
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